This may help, gained from my experience in mapping ;-) The cars are std spec then you can run '95 ron fuel with no issue. Running better fuel '97, '99 Ron will improve but not noticeably. If the car has been mapped to run '99 ron then use '99 only.... Octane boosters are for chavs lol They don't increase performance enough to worry about. You may aswell run '99 fuel. Or get it mapped :-)