the only reason someone should use a extinguisher is as a last resort to save life, you have maybe 5 seconds of use from little extinguishers, if you spend any time undoin and looking for a extinguisher it will be that much more time that either you or your passenger could get clear, so lets say you have an engine fire and you mess with the front latches and then lift the hood and have a nice flashover or explosion since you are not dressed for the fire or heat anyway and your itty bitty extinguisher has minimal range to begin with, if you have a fire get away and call someone who is trained for auto fires, your life is worth more than any viper, unless you have a 20 pound extinguisher on board that is easily accessable and is inspected monthly then the little ones can give a false sense of security(buy a little one and set it off and see what I mean), and make sure the class is correct for a vehicle fire ABC or F