diesel engines were designed to run on oil, and as long as yer vehicle has a BOSCH fuel pump as aposed to a LUCAS pump it'll be fine, i make bio diesel out of used veg oil(from pubs and cafes)and run my 1999 hilux on it 100% and have done all winter, havent had forecourt diesel in it since october, the power is the same, the mpg is the same, its better for yer engine as it lubricates it and my carbon footprint is 100% clean, its got better emissions than a brand new car, if yer cars have a BOSCH pump it'll cope with a 50/50(winter)20/80(summer) mix of veg oil/diesel with any ill effect,cheers