thats not always the case...friends camero caught fire due to some faulty wiring to his stereo and it took literally under a minute for the flames to get about 4-6 feet above the car. almost burn him and his girl alive.
or even better - just walk away from it.It's only tin and rubber. Carrying a fire extinguisher is nearly as dangerous as carrying pepper spray - you're going to be tempted to use it and it's almost inevitably going to get you in trouble.Get out early and get out fast and that's from a trained fire-marshal.