Most car fires do not actually involve the entire gasoline tank catching alight; as the gas tank is well-protected and not particularly near sources of ignition

Most car fires do not actually involve the entire gasoline tank catching alight; as the gas tank is well-protected and not particularly near sources of ignition. An engine bay fire is much more common. If gasoline is spilled, foam works well to extinguish it and keep it from igniting. Once a gasoline fire is out and cool, it is going to stay that way, Lithium-ion battery fires are self-sustaining thermal runaways. You cannot put out such a battery fire by smothering it; it does not need oxygen from the air. All you can do is try to keep it cool by running water on it. Even after such a fire seems cool, it can reignite unexpectedly. The actual gross volume of energy is not necessarily what makes fighting a fire dangerous or not; it's the unpredictability. Firefighters may be more worried about compressed gas-strut explosions (from hatches, hoods etc) than they are about the gas tank exploding.