I was taught to run away from your own car on fire, there is not enough time to locate what you need, just get out.

If it is someone else's car pop, not open, the bonnet (hood) and blow the extinguisher through the gap until it is empty, but be prepared, it will probably not be enough. Leave the opening of the bonnet to the professionals. Don't touch a cabin fire.

Last year a car in the road outside stopped with a fire under the bonnet, I dumped a 2kg CO2 extinguisher in to no effect then got a 6kg powder which did the job. By then the engine was a right off, just about everything non-metal melted.