FYI: You do NOT need to do the first 32 levels with every vehicle to get the 2nd hard badge. You just need to do any 32 levels. Thus you can save time with the first levels of the classics.
Fuel is NOT as it is supposed to be (gas != fuel consuming)!
Instead fuel is time. Just press the gas once at start and watch the fuel go down. So there is no fuel saving mode while in air or something.