Being a fireman for 25 years I say good for you to have something with you. Either for you or your fellow man.
I had an old POS Dodge employer owned work truck that caught on fire. The fuel line leaked onto a spark plug wire that evidently had cracks in it (truly an old pos). I caught it early as I smelled melting/burning and was able to mat out the flame a bit with gloves until someone with an extinguisher in their car stopped and put out the flames.
I have learned to keep an extinguisher as well as a jump starter and air compressor in my personal vehicles after that. I have helped roughly a dozen people with either jump starts or temp inflation offlat tires to get them to a tire store. Never had to use it for myself. I hope I never use the extinguisher, but in a trapped situation (mine or another driver) I know I would regret not having it.