Some of the other folks pointed out the vapors possible in a fuel tank. I’ll add that I had a coworker who had been an explosives disposal fella, and he used to get twitchy if the tank in our car dropped under half. He said it was a relatively small but definitely larger-than-our-car bomb ready to go off. I’d trust his reckonings on that one. Plus, there are parts of a car that, even if its just burning, will explode, such as the tires. I had a single tire blow as I walked around a burning car, and I would not have been amiss in describing it as a small bomb going off.