The fuel needed to power up some means of transportation can be quite tough to find, so it's best if you don't go around wasting everything just to take your new bike for a ride. It's a difficult resource to gather, and can be looted from gas stations or traded in survivor camps. If you want to go by car, always have a toolkit and a bicycle in the trunk. You can never be too cautious, right? It's best if you prevent the inevitable by having some other means of transportation in case you didn't pay attention to the fuel or didn't anticipate properly the needed amount.