I used a dry powder type, on an old ute that was hastily abandoned as it had started to burn while the bloke was driving it.

The output of the extinguisher was pathetic and only subdued the fire for a moment which would have been enough to evacuate any passengers. Luckily a quick thinking worker in a nearby factory used their fire hose extinguish the flames.

Since then, I give any powder type a good knock and shake every couple of weeks to make sure the powder doesn't settle and become useless. Because my current extinguisher is lying horizontal on the floor I rotate it every now and then.