FUEL

Vehicles are unlocked to the garage by winning career races. You will then have to use your fuel to buy them. I would recommend only buying the cars you need when you first start out as the fuel is needed to buy vehicles for certain challenges. There are going to be some races that you find really hard so this is the perfect time to use your fuel to buy the best vehicle for that specific race. There is also bonus cars unlocked after certain career races; these are marked on the map as a purple arrow. Exactly like the Doppler Trucks you need to hunt them down and knock into them to unlock them.