It depends if the petrol lasted you 1 hour - real time, I can't see a problem maybe they could sort it like this
Excelent cars - Cheetah, Infernus last 35 minutes
Sentinel - last 45 minutes
Crappy cars last 60 minutes,
I don't think may people will drive a car for more than 35 minutes so it should be OK this way.
I like that idea.