Probably getting to be an old thread now but when we had our 2015 Peugeot based motorhome I asked the question of a local Peugeot dealler who pointed me to the handbook. It stated something along the lines that a vehicle used for arduous tasks such as ambulances and taxis (heavy loads, starting from cold, lots of short journeys etc) should have an annual oil change. Sadly I don't have the vehicle now so cannot verify this but on a side note, I change the oil and filter on our vans every year. Its like £100 at the dealer - not alot for considering what people are paying for motorhomes at present.