Alan D Posted August 2, 2011 Share Posted August 2, 2011 I recently filled up at a different brand filling station and paid 3 pence more per litre than usual but then I was surprised to get 3 miles per gallon more on the fuel consumption. I have tried this on 2 fill ups on my regular run, perhaps someone smarter than me can work it out as I think I am better off paying more for the fuel and getting a longer range into the bargain. Can`t be right can it? I am usually a tightwad and look for the cheapest price, if my remaining 2 braincells are correct I have been wasting my time. Alan. Link to comment Share on other sites More sharing options...
lennyhb Posted August 2, 2011 Share Posted August 2, 2011 Unless you tell us the figures there is no maths to work out. 8o| Link to comment Share on other sites More sharing options...
Alan D Posted August 2, 2011 Author Share Posted August 2, 2011 OK, we are talking petrol prices here. I usually pay £1.33 a litre and get 34 mpg, I now pay £1.36 per litre and get 37mpg. The way I have worked it out its cheaper to pay the higher price overall and get a longer range on a tank full. Any better ? Alan. Link to comment Share on other sites More sharing options...
lennyhb Posted August 2, 2011 Share Posted August 2, 2011 At 1.33/34mpg = 17.8p/mile At 1.36/37mpg = 16.7p/mile Over 10,000 miles you will save £110 Link to comment Share on other sites More sharing options...
Alan D Posted August 2, 2011 Author Share Posted August 2, 2011 Thanks, and it`s just as I suspected so my local guy will be getting more trade from me instead of driving past to get cheaper pump prices. The comparison was with 2 leading fuel companies and I was shocked at the increased mpg, I shall try again with the supermarkets to test their figures. After that I will have a look at diesel as this is an area I just assumed all fuel was compatable and filled up with the cheapest. With a 22 gallon tank I think it`s time I took an interest. Alan Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 2, 2011 Share Posted August 2, 2011 But, how are you calculating MPG? Car trip computers are not accurate, because they do not know how much fuel you actually added, and in the "instant read out" mode, only tell you approximate consumption at that point in time. Calculating consumption from the amount of fuel added, divided by miles covered since last fill, is also inaccurate for single fills, because it is virtually impossible to re-fill to exactly the same extent each time. If the car is slightly different in level, the amount of fuel added to "full" will vary, due to air trapped in the tank. Also, if your journeys vary due to traffic density, or routes selected, one tankful may well give more MPG than another for these reasons, plus use of aircon will increase consumption, hot dry weather ditto, and using lights more/less, and even tyre pressures, will also have their effect. In short, under real life conditions, I think there are too many variables for reliable results to be gained. Best way to improve MPG, is to start with a fuel efficient car! :-) But, if you want to improve accuracy, you could take total fuel added over, say, 5 fills, divided by total mileage covered over the same period, and then switch fuels, and repeat the process over 5 more fills. It would more or less eliminate the variables to do with filling, and should help "smooth" out some of the others. Link to comment Share on other sites More sharing options...
Alan D Posted August 2, 2011 Author Share Posted August 2, 2011 OK, will do. But has anyone else noticed better economy with different brands of fuel? Alan. Link to comment Share on other sites More sharing options...
donna miller Posted August 2, 2011 Share Posted August 2, 2011 Alan D - 2011-08-02 3:27 PM OK, will do. But has anyone else noticed better economy with different brands of fuel? Alan. Oh no, do you know what you've just unleashed by asking that question. :D Link to comment Share on other sites More sharing options...
rolandrat Posted August 2, 2011 Share Posted August 2, 2011 I think the best way to check your mpg is to neck the tank after each journey, we always do, we run an old 406 Peugeot common rail diesel which averages 61mpg on a run it's an immaculate car but because of its age it's worth nothing to a dealer. Our new Golf isn't a patch on it. The 3ltr Fiat based Motorhome is another story, you can watch the fuel gauge needle going down, terrific engine with so much power but at a cost. Link to comment Share on other sites More sharing options...
Bolly1965 Posted August 2, 2011 Share Posted August 2, 2011 Perhaps it's the way the pumps are calibrated I know it's illegal for them to under deliver on a litre but perhaps they are overdelivering. Fuel pumps need to be regularly calibrated to ensure they only deliver a litre. Checking how many litres you are getting before your tank is full is an inaccurate way of working this out so perhaps we will never know Link to comment Share on other sites More sharing options...
laimeduck Posted August 2, 2011 Share Posted August 2, 2011 I think there is also a physcological aspect to this. I have a V8 Jaguar 3.2 - an old one - 1998. If I have to buy what I percieve to be more expensive petrol, I do drive a little more carefully - less right foot down, coast up to the lights & down hills etc! I can easily save 2mpg just by doing this. Same in the motorhome, I can vary the mpg by about 2mpg with driving style. However, in my overpowered 1986 2CV "Doris" I just have foot down all the time - a necessity! :D :D & get about 45mpg no matter what. Link to comment Share on other sites More sharing options...
Guest pelmetman Posted August 2, 2011 Share Posted August 2, 2011 laimeduck - 2011-08-02 5:54 PMI think there is also a physcological aspect to this. I have a V8 Jaguar 3.2 - an old one - 1998.If I have to buy what I percieve to be more expensive petrol, I do drive a little more carefully - less right foot down, coast up to the lights & down hills etc!I can easily save 2mpg just by doing this. Same in the motorhome, I can vary the mpg by about 2mpg with driving style.However, in my overpowered 1986 2CV "Doris" I just have foot down all the time - a necessity! :D :D & get about 45mpg no matter what. A Jaguar and a 2CV8-)..................Now I know where the saying "From the sublime to the ridiculous" comes from Jeremy(lol) Link to comment Share on other sites More sharing options...
bobalobs Posted August 2, 2011 Share Posted August 2, 2011 I am also doing more miles to the gallon/litre. Traced it to the ever increasing fuel prices that have made me consciously or sub consciously drive that little bit slower and lighter on the pedal. Went through the new Hindhead tunnel last weekend and though the roadsigns said it was derestricted mostcars were travelling at 50mph. Probably because they have been so used to traffic holdups there!! Link to comment Share on other sites More sharing options...
DJP Posted August 2, 2011 Share Posted August 2, 2011 Brian Kirby - 2011-08-02 3:14 PM But, how are you calculating MPG? Car trip computers are not accurate, because they do not know how much fuel you actually added, and in the "instant read out" mode, only tell you approximate consumption at that point in time. . My Fiat X250 3.0ltr 2008 trip computer overstates by 20% So the 22.1 mpg indicated is only actually 17.68 when checked by filling from brim to brim. (Tested several times). Link to comment Share on other sites More sharing options...
rolandrat Posted August 2, 2011 Share Posted August 2, 2011 Spot on Dennis. Link to comment Share on other sites More sharing options...
lennyhb Posted August 2, 2011 Share Posted August 2, 2011 DJP - 2011-08-02 7:11 PM Brian Kirby - 2011-08-02 3:14 PM But, how are you calculating MPG? Car trip computers are not accurate, because they do not know how much fuel you actually added, and in the "instant read out" mode, only tell you approximate consumption at that point in time. . My Fiat X250 3.0ltr 2008 trip computer overstates by 20% So the 22.1 mpg indicated is only actually 17.68 when checked by filling from brim to brim. (Tested several times). My 2.3 reads low by 2% i.e. reading 28mpg actual 28.5 Link to comment Share on other sites More sharing options...
laimeduck Posted August 2, 2011 Share Posted August 2, 2011 pelmetman - 2011-08-02 6:02 PMlaimeduck - 2011-08-02 5:54 PMI think there is also a physcological aspect to this. I have a V8 Jaguar 3.2 - an old one - 1998.If I have to buy what I percieve to be more expensive petrol, I do drive a little more carefully - less right foot down, coast up to the lights & down hills etc!I can easily save 2mpg just by doing this. Same in the motorhome, I can vary the mpg by about 2mpg with driving style.However, in my overpowered 1986 2CV "Doris" I just have foot down all the time - a necessity! :D :D & get about 45mpg no matter what.A Jaguar and a 2CV8-)..................Now I know where the saying "From the sublime to the ridiculous" comes from Jeremy(lol) So why is the Jag ridiculous? :D :D :D Link to comment Share on other sites More sharing options...
terryW Posted August 2, 2011 Share Posted August 2, 2011 I watched two French lads demonstrate the best way to get good fuel economy. It works as follows: 1. Go to a "pay@pump" 2. Insert hose into filler open filler and drain pipe. 3. Purchase set amount of fuel 4. After pump stops repeat process of draining pipe By the way the trip computer on my X250 is almost 100% accurate after 10,000 miles of comparing full tank actuals and trip records. Never known it with any other vehicle but the speedo is 10% high Link to comment Share on other sites More sharing options...
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