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All you need to know about modern engine oils

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Pinched off the subaru imprezza forum.


This is probably the longest post on this Forum but certainly one of the most interesting and relevant to all modern vehicle Owners.


It is the "FULL" unedited transcript of the article written by John Rowland (Chief R&D Chemist for Silkolene) with 40 years experience.


It is great educational reading as it is written by a Chemist, not a Salesman so totally based in facts - If you do one thing, read this, it's worth it!


I do not work for Silkolene, I'm a car enthusiast who owns an Oil Company that sells their products amongst others. I have Johns express permission to post this article to clear up as he says "the mis-information" on the internet.


Lubricating the modern engine.




Basically, to use that irritating in-word, engine lubrication is simple, and consequently boring. So I intend to treat the subject “complicatedly”, which may not be an in-word, but makes life far more interesting!


So, to take a quick look at the simple picture; the oil keeps moving parts apart, reducing friction and carrying away heat. Where there is metal-to-metal contact there are chemicals in the oil to reduce damage. Because the internal combustion process is always less than perfect, some soot is produced and this must be washed off the pistons and rings by the oil, so it has a cleaning or detergent function as well.


The trouble is, all this is just as true for Henry Ford’s original Model T engine as it is for the Subaru or any other high output motor. So where is the difference? The Model T, with 10bhp/litre at 2,000rpm and a single underhead camshaft, was filled with a thick, greenish liquid from somewhere near the bottom of the distillation colums on the Pennsylvania oilfields. It did a vague tour of the internals by guesswork (there was no oil pump) at a temperature around 50 degC, and lasted for 1,000 miles. On the plus side, some of the impurities acted as anti-wear and detergent chemicals. They didn’t work very well, but it was better than nothing. The engine wore out in around 20,000 miles, but even ordinary people, not just amateur rally drivers, were happy to put up with this.


The difference begins with the first turn of the key. The modern high-pressure pump would cavitate on the old heavy monogrades, starving the bearings for a vital couple of seconds, even in warm weather. Likewise, cam lobes would suffer as the sluggish oil found its way along narrow oil ways to the valve gear. The turbo bearing (if fitted as the handbooks say) already spinning fast, would also starve, and when it got going, how long would it be before the heat soak-back fried the primitive oil into a lump of carbon? (This was the problem with “modern” oils only 15 years ago).


So, a good oil must be quite low in viscosity even in the cold, so that it gets around the engine in a fraction of a second on start-up. On the other hand, it must protect engine components (piston rings for example) at temperatures up to 300 degC without evaporating or carbonising, and maintain oil pressure.


Unmodified thin oils simply can’t manage this balancing act. The answer is to use a mixture of thin oil and temperature-sensitive polymer, so as the thin oil gets even thinner with increasing temperatures as the engine warms up, the polymer expands and fights back, keeping the viscosity at a reasonable level to hold oil pressure and film thickness on the bearings. This is called a multigrade.


But, this is all too basic! What I have just written was and is relevant to a 1958 Morris Minor.


The questions that Subaru owners need to ask are: “Will this thin oil evaporate and be drawn into the intake manifold (via the closed circuit crankcase ventilation), leading to combustion chamber deposits and de-activated catalysts?” and “Will the polymer shear down at high engine revolutions and high temperatures, causing low oil pressure and component wear?” and “Will it carbonise on the turbo bearing?” These are 21st century questions which cannot be answered by a basic 1990’s approach.


BUT! Before we head into more complications, some figures………


The SAE Business (American Society of Automotive Engineers)


Viscosity is the force required to shear the oil at a certain speed and temperature. Oils work because they have viscosity; the drag of a rotating part pulls oil from a low-pressure area into a high pressure area and “floats” the surfaces apart. This is called “hydrodynamic lubrication”, and crank bearings depend on it. In fact a plain bearing running properly shows literally no metal-to-metal contact. Experimental set-ups have shown that electrical current will not flow from a crank main bearing to the shells. Also, the energy loss due to friction (the co-efficient of friction) is incredibly low, around 0.001. So for every kilogram pulling one way, friction fights back with one gram. This is very much better than any “dry” situation. For example, the much over-rated plastic PTFE has a co-efficient of friction on steel of 0.1, 100 times worse than oil.


Oil viscosities are accurately measured in units called “Centistokes” at exactly 100 degC. These fall into five high temperature SAE catagories:-


SAE No. 20 30 40 50 60

Viscosity Range 5.6 - <9.3 9.3 - <12.5 12.5 - <16.3 16.3 - <21.9 21.9 - <26


A decent quality oil usually has a viscosity that falls in the middle of the spec, so a SAE 40 will be about 14 Centistoke units, but SAE ratings are quite wide, so it’s possible for one 40 oil to be noticeably thicker or thinner than another.


When the polymer modified multigrades appeared, a low temperature range of tests were brought in, called “W” for winter (it doesn’t mean weight). These simulate cold starta at different non-ferrous monkey endangering temperatures from –15 degC for the 20w test to a desperate –35 degC for 0w. So, for example, an SAE 5w-40 oil is one that has a viscosity of less than 6600 units at –30 degC, and a viscosity of about 14 units at 100 degC.


Now, those of you who have been paying attention will say “Just a minute! I thought you said these multigrade polymers stopped the oil thinning down, but 6600 to 14 looks like a lot of thinning to me!”. Good point, but the oil does flow enough to allow a marginal start at –30 degC, and 14 is plenty of viscosity when the engine is running normally. (A lot more could damage the engine. Nobody uses the 24 viscosity SAE 60 oils any more.) The vital point is, a monograde 40 would be just like candle wax at –30 degC, and not much better at –10 degC. It would even give the starter motor a fairly difficult time at 0 degC. (At 0 degC, a 5w-40 has a viscosity of 800 but the monograde 40 is up at 3200!)


Another basic point about wide ranging multigrades such as 5w-40 or 0w-40 is that they save fuel at cruising speeds, and release more power at full throttle. But complications arise……..


Building a good oil


A cave may not be the best place to live, but it’s ready-made and cheap. This is the estate agent’s equivalent of an old style monograde oil. Or you could get Hengist Pod to fit a window and a door; this is moving up to a cheap and cheerful mineral 20w-50. But an architect-designed “machine for living in”, built up brick by brick, is an allegory of a high performance synthetic oil.


It is impossible to make a good 5w-40, or even 10w-40, using only mineral oil. The base oil is so thin, it just evaporates away at the high temperatures found in a powerful engine that is being used seriously. Although there are chemical compounds in there to prevent oil breakdown by oxygen in the atmosphere (oxidation) they cannot adequately protect vulnerable mineral oil at the 130 degC plus sump temperatures found in hard worked turbocharged or re-mapped engines.


Synthetics are the answer. They are built up from simple chemical units, brick by brick so as to speak; to make an architect-designed oil with properties to suit the modern engine.


But sometimes, if you look behind the façade, there is a nurky old cave at the back! This is because the marketing men have been meddling!


The Synthetic Myth


What do we mean by the word “synthetic”? Once, it meant the “brick by brick” chemical building of a designer oil, but the waters have been muddied by a court case that took place in the USA a few years ago, where the right to call heavily-modified mineral oil “synthetic”, was won. This was the answer to the ad-man’s dream; the chance to use that sexy word “synthetic” on the can….without spending much extra on the contents! Most lower cost “synthetic” or “semi-synthetic” oils use these hydrocracked mineral oils. They do have some advantages, particularly in commercial diesel lubricants, but their value in performance engines is marginal.


TRUE synthetics are expensive (about 6 times more than top quality mineral oils). Looked at non-basically there are three broad catagories, each containing dozens of types and viscosity grades:-


PIB’s (Polyisobutanes)


These are occasionally used as thickeners in motor oils and gear oils, but their main application is to suppress smoke in 2-strokes.


The two important ones are:




All jet engines are lubricated with synthetic esters, and have been for 50 years, but these expensive fluids only started to appear in petrol engine oils about 20 years ago. Thanks to their aviation origins, the types suitable for lubricants (esters also appear in perfumes; they are different!) work well from –50 degC to 200 degC, and they have a useful extra trick.

Due to their structure, ester molecules are “polar”; they stick to metal surfaces using electrostatic forces. This means that a protective layer is there at all times, even during that crucial start-up period. This helps to protect cams, gears, piston rings and valve train components, where lubrication is “boundary” rather than “hydrodynamic”, i.e. a very thin non-pressure fed film has to hold the surface apart. Even crank bearings benefit at starts, stops or when extreme shock loads upset the “hydrodynamic” film. (Are you listening, all you rally drivers and off road fanatics?)


Synthetic Hydrocarbons or POA’s (Poly Alpha Olefins)


These are, in effect, very precisely made equivalents to the most desirable mineral oil molecules. As with esters, they work very well at low temperatures, and equally well when the heat is on, if protected by anti-oxidants. The difference is, they are inert, and not polar. In fact, on their own they are hopeless “boundary” lubricants, with LESS load carrying ability than a mineral oil. They depend entirely on the correct chemical enhancements.


PAO’s work best in combination with esters. The esters assist load carrying, reduce friction, and cut down seal drag and wear, whilst the PAO’s act as solvents for the multigrade polymers and a large assortment of special compounds that act as dispersants, detergents, anti-wear and oxidant agents, and foam suppressants. Both are very good at resisting high-temperature evaporation, and the esters in particular will never carbonise in turbo bearings even when provoked by anti-lag systems.


Must Have MORE Power!


Motorcars are bought for all sorts of reasons, but enthusiasts like lots of power. To get more power, a lot of fuel must be burnt, and more than half of it, sadly, gets thrown away as waste heat. For every litre of fuel burnt, 60% of the energy goes as waste heat into the exhaust and cooling system. A turbocharger can extract a few percent as useful energy and convert it into pressure on the intake side, but only 40-45% is left, and only 25% actually shows up as BHP at the flywheel. 6% goes in pumping air into the engine, 6% as oil drag losses and 2-3% as engine friction. The oil deals with 97% of the friction; so reducing the remaining few percent is not easy. If you doubt that even ordinary oil has a massive effect, take a clean, dry 200 bhp engine, connect it to a dyno and start it up. It will only make 1 bhp for a few seconds. Now that’s real friction for you!


Oddly enough, people get starry-eyed about reducing friction, especially those half-wits who peddle silly “magic additives”, which have not the smallest effect on friction but rapidly corrode bearings and wallet contents. In fact, even a virtually impossible 50% reduction in the remaining engine friction would be no big deal, perhaps one or two bhp or a couple of extra miles per gallon.


Even More Power!


He place to look for extra power is in that 6% lost as oil drag. In a well-designed modern motor, the oil doesn’t have to cover up for wide clearances, poor oil pump capacity or flexy crankshafts, so it can be quite thin. How thin? Well take a look at these dyno results.


A while ago now, we ran three Silkolene performance oils in a Honda Blackbird motorcycle. this fearsome device is fitted with a light, compact, naturally aspirated 1100cc engine which turns out 120+ bhp at the back wheel. The normal fill for this one-year-old engine was 15w-50, so the first reading was taken using a fresh sump-fill of this grade. (The dyno was set up for EEC horsepower, i.e. Pessimistic)



Max Power 127.9 bhp @ 9750 rpm

Torque 75.8 ft-lbs @ 7300 rpm


After a flush-out and fill up with 5w-40 the readings were;



Max Power 131.6 bhp @ 9750 rpm

Torque 77.7 ft-lbs @ 7400 rpm


Then we tried an experimental grade, 0w-20 yes, 0w-20! This wasn’t as risky as you may think, because this grade had already done a season’s racing with the Kawasaki World Superbike Team, giving them some useful extra power with no reliability problems. (But it must be said, they were only interested in 200 frantic miles before the engines went back to Japan)



Max Power 134.4 bhp @ 9750 rpm

Torque 78.9 ft-lbs @ 7400 rpm


In other words, 3.7 bhp / 2.9% increase from 15w-50 to 5w-40, a 2.8 bhp / 2.1% increase from 5w-40 to 0w-20 or a 6.5 bhp / 5% overall. Not bad, just for changing the oil! More to the point, a keen bike owner would have paid at least £1000 to see less improvement than this using the conventional approach of exhaust/intake mods, ignition re-mapping etc.


Am I recommending that you use 0w-20 in your Subaru’s? Well, perhaps not! The 5w-40, which is a “proper” PAO/Ester shear-stable synthetic, will look after a powerful engine better than a heavier viscosity “cave at the back” conventional oil, and provide a useful extra few BHP.



And useless oil additives.


Don't use them, here's some reasons why you will be in effect wasting your money.






This is the transcript of an AA article published in Motor May 10th 1986.




The widely-advertised oil additive Slick 50 has been soundly slammed by the AA’s Technical Services.


The AA claim that their tests show Slick 50 provides no fuel savings when it is added to a cars engine oil – and there is no evidence of any other benefits under normal operating conditions.


The AA have made no press or public announcement of their report, but have produced a leaflet for the benefit of any paid-up members who apply for one. An AA member on Motor’s staff applied for a report in the normal way.


The report states that whilst there is no evidence the product will do harm to the engine, one good point is that most of it will be very rapidly removed by the oil filter. “At about £12 per treatment”, say the AA, “it is a very expensive way of coating your oil filter element”.


The AA performed tests by taking three identical cars and carefully running them in, splitting the driving equally among their test drivers. Oils were changed at 1500 miles, the cars were run a further 500 miles to stabilise the oils’ viscosity, the cars’ tuning was carefully checked and steady speed fuel consumptions and power outputs were measured.


The report says: “The procedure is so sensitive that, for instance, leaving the headlamps of the car switched on will make a nonsense of the results due to the extra drag of the charging system”.


Engineers added Slick 50 to two of the cars in the recommended way at 3000 miles.


After a further 2000 miles, further dynamometer tests were carried out. “One car should show the sort of gradual change expected of a car in good condition” says the report, “whereas two should show a noticeable improvement . Here came the big disappointment. After our several months of careful testwork, we could not distinguish any difference between the three cars.”


The AA claimed that all cars were performing well, but performance was remarkably consistent , within a few percent.


The AA say that a detailed examination of the claims made for the product will explain what happens when Slick 50 is added to an engine. Of one gallon of petrol burnt in an engine, says the report, some 60 percent of the energy will be lost as heat from the exhaust and cooling system. That leaves 40 percent and some 25 percent is used to drive the car and its accessories. The remaining 15 percent goes to losses such as pumping air into the engine (6 percent) and some 9 percent is lost as engine friction. Of that 9 percent, 6 percent is lost in churning the oil and only 3 percent of the total input goes into the sort of “boundary” friction that a solid lubricant could affect. “If tests of Slick 50 did show a 16 percent decrease in this friction, as claimed in current advertisements”, says the report, “it would only affect the car’s overall consumption by a half of one percent”.


The AA also claim that their tests show there is no evidence that Slick 50 produces a surface layer on the engine wearing surfaces, let alone one that could last for 100,000 miles.




On questioning John Rowland, I received the following reply.








The AA report encapsulates my opinion of Slick 50, it is an expensive way of blocking your oil filter, Believe me, it does precisely nothing beneficial. It has been proven time and time again that it just blocks oil filters and oilways.




For all other “magic” additives, most are based on 1930’s technology corrosive chlorinated paraffins. (synthetic anti-seize compounds originally made 70 years ago. They are cheap, toxic and corrosive. We use them in certain types of cutting oil!) Do not touch them with somebody else’s bargepole!




UCL’s (upper cylinder lubricants) on the other hand can be useful. After all, 2-strokes in effect run entirely on UCL. So……the best UCL’s are 2-stroke oils! I always tell people to use a decent 2-stroke at 0.5% or 1%, because they are superior to the UCL’s sold as UCL’s if you get my drift. A litre of Super 2 Injector or Comp-2 will be better than a cupful of cheap mineral oil dyed red (no prizes for guessing the name) any day.




Vee engines (twins, to V8’s) benefit from UCL’s because the upper walls of the RH cylinder bank, looking from the front, always run dry. Think about it!





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Here is even some more bedtime reading for you. Now this is much better written answers - same guy...more up to date.





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oilman21-01-2008, 12:40 AM

But not from us this time!


We get asked many oil related questions every day and decided to put some of the most frequently asked ones to an Oil Expert called John Rowland. He has been the Chief R&D Chemist for Fuchs/Silkolene for many years and previously developed ahead of their time ester based oils for the RR Jet industry. What he doesn’t know about oil is not worth knowing in our opinion!

Even though some of these topics may have been covered before here, this post is well worth reading.


1) How is an oil manufactured; transformed from the black sludge that comes out of the ground, into the nectar-like substance we pour into our cars and bikes?


Crude oil, which is usually very thin, (contrary to popular belief!) is distilled into light and heavy fractions, with several intermediate ones. (The evil left-overs are used to fuel the 15 million cc/40RPM diesels in the giant oil tankers that bring the crude to the refinery.)

The lighter fractions, usually more than 90% of the original crude, are converted into petrol and diesel. Some of the heavier oils, (still dark and smelly!) go through several processes to clean them up and remove wax. Out of about a dozen oily products 4 clear, bright amber oils are commonly used to blend modern engine and gear oils. These are roughly equivalent to SAE 10, 20, and 30 engine rating and 140 gear rating. Oil refineries also produce all sorts of gases and chemical compounds which can be used to build up 'tailor made' lubricants: synthetics!


2) What are the most important substances added to the refined base oils? What do they do?


In the Dark Ages, engines used blends of refined mineral oils 'straight', with nothing added. The trouble was, even in the slow-revving engines of 80 years ago the oil didn't last very long, and the engines didn't either.

Black sludge and corrosion were the killers, and both were tackled in the 1950s with detergent and antioxidant chemicals. (When I was a lad, I used to visit a mate of my Dad's who rebuilt the very popular side-valve Ford engines. The thick crap inside these things was unbelievable! The valve tappets were moving in holes in solid blocks of carbon!) The detergents washed the carbon from fuel combustion off the bores and out of the ring grooves, and at the same time reduced bore and piston ring corrosion.

The antioxidants stopped the oil reacting with oxygen in the air, which cut acid sludge formation which in turn reduced corrosion and oilway blockages. Some antioxidants had the useful side-effect of reducing wear as well. This added up to longer oil and engine life, both improving about three times. (Straight oil had to be changed every 1000miles, and even lightly-stressed engines running on it were ready for a full overhaul at 15-20,000.) OK, I admit there were design and metallurgical improvements, but they needed that vital 'liquid component' to be fully effective.

Later came dispersant compounds which held the carbon as tiny particles in the oil which didn't settle out anywhere, and slipped through the oil filter as if it wasn't there.(Solid bits in well-used modern oil are about 1/1000mm

across; the pores in an oil filter are at least 15 times bigger.)

The other big problem with oil used to be cold starting. It was usual to have SAE 20 Winter or 'W' grades, and SAE 30 or 40 Summer grades, and even the so-called Winter types would defeat the starter in serious cold weather. Unfortunately, oil is very thick when it's cold, and very thin when it's hot. To have an oil thick enough to look after a

hard working engine, you had to use a grade which was too thick when it was cold.


The answer was (and is) multigrade! What was needed was an oil that behaved like a 20 'W' grade in the cold, but only thinned down to a SAE 40 or 50 when really hot; yes, 20W/50! This can be done by mixing thin oil with thick polymers based on plastics and synthetic rubbers; these don't do much in the cold, but as the oil warms up they unwind and thicken it up to some extent. The oil still thins down, but not as quickly as a polymer-free or monograde type.

Multigrades started to catch on around 1960, but these pioneer types were easily ruined by mechanical shear effects, more so in gearboxes than engines. These days the better quality polymers resist shear even in combined engine/transmissions, so it is essential to use good quality shear-resistant types in a gearbox fed by the engine (such as the traditional mini!), which gives its oil a hard time in both engine and gearbox.

Incidentally, there are large amounts of these additives and polymers in there, it's not just 'a little bit of this, a little bit of that'! A good quality mineral 10W/40 can be 80% base 20% additive chemistry, and guess which is the expensive ingredient!


3) What are the differences, in layman's terms, between mineral, semi-synthetic and fully-synthetic engine oil? (In terms of structure and performance.)


Before we get into details, the first thing to realise that there is no chalk and cheese difference between mineral and synthetic based oils. After all, the chemical compounds which make mineral engine oils so much better are themselves synthetic.

Synthetic lubricant bases are stepwise improvements on mineral oil, with more desirable properties and fewer

undesirable ones. The second important point is that there's no one thing called 'synthetic'! There are several different types of synthetic lubricant, and to say something like: 'the Supergrunt GTI TURBO must have a

full synthetic' is meaningless unless the 'expert' explains what sort of synthetic he means.

Equally, to imply that dreadful things will happen if the 1970 RV8 is run on anything other than good’ ole mineral oil is ridiculous. It may not need a 2007 synthetic, but it isn't going to come to any harm if the owner uses a 2007


The most basic type of synthetic is really a special mineral oil. Known as 'hydrocracked' bases, these are made in oil refineries by putting certain types of mineral fraction through special processing, so they cost more than the usual mineral types but not much more. They are useful because they resist evaporation at high temperatures. Although

used for years for genuine technical reasons, they are now popular with marketing men because the magic sexy word 'synthetic' can legitimately be printed on the label without spending much on the oil inside the can!

Yes, all low-cost 'synthetics' contain anything from a few percent to 20 percent (i.e. 'semi-synthetic') of special mineral oil. Using fairly simple chemical compounds or gases from oil refineries or other sources, it is possible to 'synthesise' or build up tailor-made lubricant molecules which have very desirable characteristics, such as great resistance to cold, heat, evaporation losses or excessive thinning as they get hot. These are the true synthetics, and the two that are used in engine oils are PAOs (poly alpha olefins) and esters.

Neither is cheap! PAOs are related to mineral oils, and are the ideal carriers for all the chemical compounds used in mineral oils. Because they do not gel at very low temperatures, all genuine 0W-something oils have to be based

on PAOs to pass the 0W test at a sub-arctic -35C.

Esters were originally made for jet engine lubricants, and to this day all jet oils are ester-based. Although similar in performance to PAOs, they have a valuable extra trick: they are good lubricants and help to protect metal surfaces. Esters help with transmission and valve train lubrication. 100% fully synthetic oils are actually quite rare, probably because they are very expensive to make, and even more expensive to buy.

Even so, an ester/PAO with a very shear stable multigrade polymer is the ultimate oil for high output engines that are worked hard, which means racing.


4) How does oil work? What gives it its lubricating properties? How does it 'cling on' to surfaces?


A plain bearing such as a main or big end, when spinning fast is 'floating' on a relatively thick film of oil. The metal surfaces literally do not touch. The high velocity drives a wedge of oil between the two surfaces, and the oil film supports the load, just like a water skier skimming over that very thin lubricant, water. But, when the engine slows down and stops the bearing shells drop through the film and touch the crankpins, just as the skier sinks in up to his neck when he lets go of the rope.

It is where there is metal to metal contact that lubrication, that is, something to reduce wear and seizure, is needed.

On gear teeth, valve components, and piston rings at top or bottom dead centre, there is no high speed rotation to generate 'wedge' support, so the oil films are very thin, and some metal contact is inevitable. Some fluids, even if they look thick and oily, are completely hopeless! Very pure mineral oils, and some synthetics fall into this group. They depend entirely on chemical load-carrying compounds which react with metal at high pressures and temperatures to provide very thin protective films which prevent micro-welds where metal surfaces come into contact.

Detergent and antioxidant chemicals often double up as anti-wear agents. The odd ones out are esters. These are attracted to metal by electrostatic forces and cling on when surfaces are forced into contact.




oilman21-01-2008, 12:41 AM

5) What are (or can be) the main differences between oils of the same type, i.e. what's the difference between a 'good' and a 'bad' oil?


It all comes down to honesty really.....so beware! A good oil is what it claims to be on the can. 10W/40? Does it really pass the cold test at -25C? Quite a few I've tested do not. There is usually an API spec quoted, such as API SH or SL. These are car-based, and a good basic quality guide. If absent, leave it on the shelf, and avoid lawyer-speak:

'meets the requirements of....' or 'recommended (by whom?) for use in....'.


Then there is the 'synthetic' minefield! Provided the price hasn't been pushed up by shipping an average oil 5000miles from the West coast of the USA, you get what you pay for. The best performance oils are made

in the more developed European countries, but low price buys the cheap 'modified mineral' synthetic and not much of it, with a poor multigrade polymer. As is so often the case, quality follows cost.


6) What are the likely consequences of using poor-quality oil?


Usually, these are fairly long term, except in racing. Think of the oil as a liquid component, and poor oil as a cheap pattern spare. In a road car long-term reliability and performance retention (i.e. acceleration figures below new spec., fuel and oil consumption above) are the casualties. Particularly in a high performance or racing car,

the effects can be more immediate and catastrophic.


Thanks to John for his honest and informative advice, we look forward to the next instalment!.








oilman22-01-2008, 10:01 AM



7) Some oil companies have run advertising campaigns that imply their products have special, unique qualities. Can these adverts be taken seriously?


Yes and no! Generally adverts in magazines are honest, with marketing-speak terms such as ‘Magnatec’ and ‘Electrosyntec’ really being code words for esters, which are particularly beneficial in performance engine oils. No manufacturer has any unique ‘secret’, so it’s all down to providing the best possible blend for the job at the right price, and making it clear that you get what you pay for. I personally think that the importance of shear stability or ‘stay in grade’ is not stressed enough when quality is talked about.


What is dodgy though is claiming that a mineral based oil with a few percent of modified mineral (‘hydrocracked’) synthetic is the DB’s and suitable for racing, etc. when it clearly isn’t.


Also, there is endless semantic manoeuvring and lawyer-speak around The Magic Word ’synthetic’.


For instance, a ‘synthetic’ oil is invariably semi-synthetic (’Ah! We didn’t say it was all synthetic did we?), and, if low priced, invariably the modified mineral type synthetic. It is a sad fact that you get what you pay for, but even so, stick to the reputable UK/European brands, and remember that shipping an oil half way around the world doesn’t automatically make it better than one made in your home town.


As for TV advertising…well, does anybody believe it? Due to its huge cost, a TV advertising campaign can significantly raise the cost of specialist items such as oil. Everybody assumes it’s just a few pence per gallon, but it can be pounds per gallon.)


Please can you explain the grading system? What is meant by the weight of an oil? What does 10W/40 mean for example?


Weight means viscosity, or resistance to flow. Water and paraffin flow very easily, so they are low or light viscosity. Golden syrup or 140 gear oil do not come out of the can so easily, so they are high or heavy viscosity.


Especially with oils, temperature is very, very important. An oil which looks ‘heavy’ at 20C will be very ‘light’ at 100C. People sometimes say, ‘I drained the oil when the engine was hot and it ran out like water…’ so I say, ‘Good! It’s supposed to be like that!’


The American Society of Automotive Engineers (SAE) ratings cover cold starts and ‘up and running’ viscosities. There are two sets of standards, the ‘Winter’ (W) ratings, and the 100C standard ratings. (‘W’ does not, repeat not, mean ‘weight’!)


So a 10W/40 oil has to pass a 10W cold viscosity test at -25C, and a SAE 40 test at 100C. In an oil lab there will be a refrigerated viscosity measuring device for the ‘W’ tests and another at 100C for the standard SAE tests. There are 6 ‘W’ ratings from the difficult 0W at -35C to the dead easy 25W at -10C, occasionally used in India for example!


The whole point of these Winter ratings is to assist cold starts, to get the oil circulating quickly, and to avoid power and fuel wasting drag as the engine warms up. Once it is warmed up, the 100C ratings count. There are 5 of these, 20, 30, 40, 50, and 60 although why anybody bothers with 60 in the 21st Century is a mystery to me!


Sorry folks, but I’ve got to get technical. Viscosity is measured in standard units called ‘Centistokes’, names after a Victorian engineer, Sir George Stokes, who used to time ball bearings as they sank through oil. SAE 30 for example is from 9.3 to 12.5 Centistokes, and SAE 40 follows on at 12.5 to 16.3, although most SAE 40 oils are in the middle at about 14.


Now this is something most don’t realise: engines do not know what grade of oil they’re running on. They’re not clever enough! So an engine filled with 10W/40 will be running on a viscosity of 14 at 100C, but with a sump temperature of 90C its seeing a viscosity of 18, so as far as the engine is concerned it’s running on SAE 50. Likewise, at 110C, it’s down to 11 Centistokes so it ‘thinks’ it’s on a SAE 30! (Which is preferable.)


The lesson is, do not use power and fuel-wasting thick oils in cool climates. A decent 10W/40 or even thinner is perfectly OK unless you’re running a classic with wide clearances and a slow oil pump.


Radical race cars use 1300 Suzuki Hyabusas and work them very hard. (Didn’t one take the old Nurburgring absolute record at one point?). They use our high-ester 15W/50, but that’s OK because they see oil temps around 130C! (No problem for the oil or the engine, but they do fit special oil seals.) At 130C the true viscosity is 10cSt, so the engine thinks its on a thin SAE 30, which keeps it happy.


8) What is the best type of oil to use in a road car for general use? Is fully synthetic a waste of money?


Personally I’d go for a shear-stable part ester synthetic, SAE 10W/40 or 5W/40. The ‘shear-stable’ bit (ie, a decent quality multigrade polymer) is actually more important than the ‘synthetic’ part!


If strapped, I’d go for a shear-stable mineral based oil rather than a ‘synthetic’ of dubious stability that’s probably based on modified mineral oil anyway. Unless you’re covering a huge annual mileage, genuine 100% synthetics are probably an extravagance. High mileage long-distance fans can use a light full synthetic and save on fuel and oil changes, and cut overhaul costs if things get to that stage, but more later…..


9) What are the main differences between 2 and 4-stroke oil? Why does 2-stroke oil have to be mixed with fuel?


2-stroke oil has a very short working life, straight in and out, and it gets burnt. The 2-stroke engine doesn’t have a sump full of oil and the bearings are all rollers, so there’s hardly any oil drag, hence no need for multigrades. Long term stability is obviously not a problem!


But, 2-stroke must burn off without leaving any plug-fouling or detonation-initiating deposits. The detergent and anti-wear additives used in 4-stroke oil leave hard white ash behind when they burn, just what you do not need in a 2-stroke. So 2-stroke oils use low-ash detergents and dispersants, and the better types use ester synthetics to act as anti-wear compounds.


With current environmental concerns, smoke is a sensitive issue, so most ‘road’ 2-stroke oils are now low smoke, which requires yet another type of synthetic base designed to burn off invisibly. For some rather basic but very high-revving air-cooled racing 2-strokes there’s still some sense in using blends with that marvellous anti-seize liquid, castor oil!


Due to crankcase induction and compression, the classical 2-stroke obviously cannot have an oil-filled sump, so the only way to keep an oil film on anything was to add oil to the fuel, or inject oil into the crankcase space where it could mix with the fuel vapour. There are now some engines where the fuel and oil are injected separately, but the oil is still burnt.


10) How important is it to change oil regularly? What are the implications of failing to do so?


It is only really important to change oil regularly if the engine covers a low annual mileage made up of slow, short runs. This is being cruel to the oil and the engine! The oil, regardless of its quality, gets full of fuel and water vapour, and never gets the chance to evaporate it all off with a long fast run. The consequences are corrosion, ring and bore wear. It is essential to do a change at least once a year, even if the recommended mileage hasn’t been covered. On the other hand, if you eat up the miles on long blasts the engine and its oil will love it, so with a top-quality oil it is OK to cheat a little on oil drain periods.


11) Do some types of oil (i.e. fully-synthetic) ‘wear out’ quicker than others? How important are timely oil changes? Can you rely on the frequency suggested by your User Manual?


The type of oil that is likely to give trouble after low mileage is a light viscosity type with poor shear stability, either mineral or modified mineral based. (Such as one of the USA ‘fuel economy’ oils for lazy car engines that pushed the Japanese OEMs to bring in their own oil spec.) The important thing is the shear stability; the much hyped ‘synthetic or mineral’ nonsense is a red herring.


The oils that will last the longest are the relatively rare 100% genuine synthetic shear stable types, which will easily stand twice the recommended drain period in a high-mileage high performance engine. (So in the long run they aren’t really so expensive.) Just the thing for those touring fiends who pack up and set of for the Transylvanian Alps as soon as the clocks go forward!


Of course, User Manual drain recommendations are based on a back-covering ‘worst case’ scenario of low annual mileage on poor quality oil, so they can be regarded as a very safe minimum mileage.


In the past, there used to be trouble with heavy carbon deposits and sludge around the engine with early low-detergent oils, but these days almost any oil with a good API specification will keep everything clean for 10 to 15,000 miles, so that’s the least of your worries.




oilman22-01-2008, 10:01 AM

Final part...........................


12) Does oil have to be warm to do its job properly? Is it important to warm up your engine before using at speed?


Yes, it does have to be at least warm, and preferably hot. Most people except the sort with white finger syndrome find metal at 60C too hot to touch, yet 60C is too cold for oil in an engine that’s going flat-out. The best approach is to use a good 5W/40 or even a 10W/40, and take it easy for the first couple of miles, especially in very cold weather.

For racing, a really good warm-up is essential, except perhaps with special 0W/20 low-drag race oils. The trouble is, oil pumps are very good at pushing oil out at 60PSI, but unfortunately there is only 14PSI (atmospheric pressure) pushing it in! (Even less in Katmandhu.) So it’s easy for an oil pump to pull voids or pockets of vacuum in the oil if it doesn’t flow fast enough into to uptake. This ‘cavitation’ obviously reduces the amount of oil the pump can deliver.


Also, in high-speed bearings the oil can be too thick to keep up with the high rubbing speeds reached in modern engines so the ‘wedge’ or hydrodynamic’ effect breaks down. I know it goes against common sense (whatever that is) but the faster a bearing is turning the thinner the oil should be. (A 4cm. diameter main bearing is rubbing its shells at 56 MPH at 12,000RPM! To avoid cavitation the oil need to be less 10cSt or less, which is SAE 30 if the oil happens to be at 100C, or SAE 40 if its at 110C.))

What is the difference between road and racing oils?

The days of incense-like ‘R’ oils for racing only are past, except for classics. At least as far as 4-strokes are concerned, the best synthetic types are ideal for both race and road use.


With ultra-precise components, high-pressure pumps and high engine RPM there has been a move to special synthetic low cavitation/low drag oils to release more power with no reliability loss. These can be (and are!) used in road cars, but 0W/20 is not mentioned in the user handbooks, so there is always some warranty risk. Honda is perhaps the only exception!


13) How does a high-performance oil allow the motor to produce more power?


An engine wastes fuel energy in several ways, and most of them are due to the laws of thermodynamics, which is another way of saying you can’t do much about it. But up to 6% of engine output is lost due to oil drag, made up of pumping losses and viscous drag between moving components. The transmission is included in this.


Provided wear and friction are kept down, there are real gains to be made by using a ‘tough’ but low viscosity oil. Surprisingly, frictional losses are low, down at 3% or less even with conventional oils, so there are few gains to be made here.


I have actually seen this extra power output on the dyno! A very experienced operator in Peterborough who does a lot of test work for Lord Emap used his own year-old Honda Blackbird, with the first run on his favourite 15W/50 high-ester synthetic. 128BHP.


Then we changed to a 5W40 high ester synthetic. (So it wasn’t an unfair comparison with B & Q 15W/50!) This time we saw 131.6BHP with a corresponding torque increase.


Finally we went to a new (at that time) 0W/20 special synthetic and 134.4BHP appeared! Even the boss was impressed! Later trials in different race and road engines showed this level of improvement was no fluke, so it really does work; and, with the right chemistry to look after the engine and transmission internals, there’s no down side of increased wear.


14) Why do some engines consume oil? Is this a problem?


Large air-cooled engines or classics with wide piston clearances, or very highly stressed liquid-cooled engines which flex under load, or which use ultra-light pistons with the minimum number of rings are likely to be oil users. There is little that can be done about it. Unfortunately, burnt oil tends to leave hard deposits in the combustion chambers which can initiate pre-ignition, so more frequent top overhauls are usually necessary.

Occasionally, touring engines will use oil for no apparent reason. This is often due to the oil level rising in the crankcase due to air retention, leading to oil loss through the breather. The answer is to move to a lighter grade of oil to improve air release.


15) If you need to top up your engine oil, how important is it to use exactly the same brand and type?


Not very important at all. Unfortunately, due to ‘arse covering’ reasons we cannot print this advice on the can! Although officially all manufacturers advise against mixing different makes and grades, in fact there is very little chance of any harm being done, even if one is a mineral 20W/50 and the other is a 5W/30 synthetic. Obviously, avoid this if you can, but do not panic if there’s no other alternative. Just don’t mix 2 stroke and 4-stroke oil!


16) There are all sorts of additives available which are supposed to improve ordinary oil and reduce friction, improve power output etc. Are they worth a try?


Oil is already a very advanced and deeply researched fluid which does not need any ‘enhancement’. There is no secret formula out in the backwoods that the mainstream lubricant chemists do not know about; but there are plenty of half-baked ideas and gullible people out there!


These wonder additives are usually 1930s chlorinated paraffins, long obsolete gear oil additives which should have disappeared in the 1950s, but they keep turning up as ‘Xxtrasuperlube ZX3’ with a mark-up of several thousand percent. They actually corrode engine and transmission internals, so they do far more harm than good.


Others depend upon the total myth that PTFE powder coats engine internals and reduces friction. It doesn’t do anything or the sort. It just blocks the oil filter. The AA tested one of these overpriced PTFE concoctions (‘Quick 60’ or something) very thoroughly back in the 80s. They stated: ‘This is an expensive way of coating your oil filter’.


So there we have it, would just like to thank once again John Rowland (R&D Chemist) for taking the time to provide these answers to questions that we are frequently asked.


The Opie Oils Team.





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Hello all,


That was fascinating but it raises a couple of questions for me....


Before I begin I should stress that while I have lots of experience in the use of lubricants and an engineering background, I can't profess to be an expert in that field.


The comments about oil additives would seem to be unfair. While I don't use them myself, I think the expert and the AA report have missed the point somewhat in that many additives have been marketed as a way of reducing wear and oil consumption on older, higher mileage engines; and as yet there has been no conclusive proof that they don't do anything other than these tests conducted on carefully run in, virtually new engines. I would suggest that the reason why the AA findings have not been generally published is due to fear of litigation by the manufacturers of additives.


Personally, I would just stick a thicker oil in an engine that was past it's best or fix it properly if it was still required to do a job reliably but there is a chance that one or more of the additives on sale that do not rely on PTFE to reduce friction but cleaning agents or thickeners may have some benefit on older engines.


I don't know for sure, but I think it is unfair to debunk the whole industry based on tests carried out on healthy, virtually new engines. I doubt that Slick 50 or any of the other brands have claimed their product was supposed to do anything remarkable in those conditions.


The big question that could do with a proper answer now is what precisely a 'Low SAPs' oil does and how much we really need it in our modern engines? Is it another expensive snake oil or is there more to it? I think it's just an oily fix for a lazy and unimaginative design of emissions treatment; but what would i know?



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Guest 1footinthegrave
Certainly can vouch for the "bed time reading " I fell asleep after about three paragraphs, and it's nowhere near bed time. :-S
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A discussion on the PistonHeads forum about oil additives...




and a 20-years-old piece that may be interesting




I remember adding Molyslip to the engine oil of my first two Golf GTis on the recommendation of GTI Engineering who were then the acknowledged experts for those vehicles. I'm pretty sure I obtained the stuff from a VW dealership and (I think) it was VW approved. Not sure it did any good, though it didn't do any harm to either car. I also added a Molyslip additive to the cars' gearboxes (again at the recommendation of GTI Engineering) and there's no doubt whatsoever that this lightened up the gear-change action significantly.

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euroserv - 2013-01-04 3:16 PM


Hello all,


That was fascinating but it raises a couple of questions for me....


Before I begin I should stress that while I have lots of experience in the use of lubricants and an engineering background, I can't profess to be an expert in that field.


The comments about oil additives would seem to be unfair. While I don't use them myself, I think the expert and the AA report have missed the point somewhat in that many additives have been marketed as a way of reducing wear and oil consumption on older, higher mileage engines; and as yet there has been no conclusive proof that they don't do anything other than these tests conducted on carefully run in, virtually new engines. I would suggest that the reason why the AA findings have not been generally published is due to fear of litigation by the manufacturers of additives.


Personally, I would just stick a thicker oil in an engine that was past it's best or fix it properly if it was still required to do a job reliably but there is a chance that one or more of the additives on sale that do not rely on PTFE to reduce friction but cleaning agents or thickeners may have some benefit on older engines.


I don't know for sure, but I think it is unfair to debunk the whole industry based on tests carried out on healthy, virtually new engines. I doubt that Slick 50 or any of the other brands have claimed their product was supposed to do anything remarkable in those conditions.


The big question that could do with a proper answer now is what precisely a 'Low SAPs' oil does and how much we really need it in our modern engines? Is it another expensive snake oil or is there more to it? I think it's just an oily fix for a lazy and unimaginative design of emissions treatment; but what would i know?



Here you are Nick. It's supposed to stop you harming the DPF and CAT' apparently.


Australia is experiencing a surge of European produced,

diesel powered motor vehicles requiring a low SAPS

(Sulphated Ash, Phosphorus, Sulphur), synthetic blend

or full synthetic motor oil. European OEMs have been

driving European Union legislation (Euro IV) to reduce

harmful emissions from diesel powered vehicles. In turn

vehicle manufacturers with new fuel efficient engines

and treatment systems required new engine lubricants.

It is a fact that almost one-third of new cars sales around

the world occur within the European Union (18 million

vehicles sold in 2006*) – making it one of the largest car

markets in the world. Although this figure may seem

irrelevant to Australians alike, the European Union

produces almost 70 million new motor vehicles each

year with many being exported around the world,

including to Australia.

Known by the acronym, ACEA, the European Automobile

Manufacturers Association alongside with the European

Commission have set targets to reduce CO2 (carbon

dioxide), NO (nitrogen oxide) and particulate levels

which are emitted into the atmosphere by all types

of vehicles powered by fossil fuels.

“The introduction of Euro IV

regulations in 2005 has seen many

OEMs modify and develop new

engine designs and emissions

systems to meet these regulations”,

says Valvoline’s Regional Technical Manager, Ed Kopinski.

OEMs have reduced harmful emissions from diesel

powered vehicles through the installation of after

treatment devices such as diesel particulate filters (DPFs).

“To maintain the efficiency and performance of these

anti-pollutant devices, new technology, low SAPS

motor oils needed to be developed. Low SAPS means

that the motor oil is to contain lower concentrations of

Sulphated-Ash, Phosphorus and Sulphur when compared

to traditional lubricant technologies – all of which can

be detrimental to the after treatment devices which are

installed to protect both the environment and our health

from harmful emissions”, says Kopinski.

Represented by a large group of European engine

manufacturers, ACEA have developed an additional

category just to represent vehicles requiring a low or

controlled mid SAPS motor oil. Suitable for diesel

powered vehicles fitted with DPFs, a ‘C’ category

was developed with C1, C2 and C3 classifications.

Valvoline’s SynPower MST SAE 5W-30 is a full synthetic

motor oil designed for use in vehicles fitted with catalytic

converters or DPFs. It is a mid SAPS formulation meeting

both the ACEA C3 and API SL/CF specifications. The

lubricant is also suitable for exhaust gas recirculation

(EGR) systems and can be used in applications that offer

long drain intervals of up to 30,000km. The low viscosity

formulation also means that Valvoline SynPower MST

SAE 5W-30 offers enhanced fuel efficiency and, with

a low pour point, it results in an easy cold start.

European motor vehicles fitted with anti-pollutant

devices are expected to continue to increase in Australia

and the demand for low or controlled mid-SAPS motor

oil will follow.

For technical information please contact the Valvoline®

Technical Hotline on 1800 804 658. Monday to Friday

8:30am to 4:30 pm EST.




The cross section image shows a diesel particulate filter (DPF) with

sulphated ash deposits. Motor oil containing high levels of SAPS can clog

the DPF which can contribute to poor performance and increased fuel




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