While any fire extinguisher is better than none.
I have some experience with car fires.
a 1KG fire extinguisher will be out of juice before you even get started.
get a 2KG with a nozzle as you will be able to poke the nozzle to where the fire is (you dont want to pop the hood to get at a fire as the hood will be too hot to touch and the latch too hot to operate, and it takes too long.
get one like this
and aim the nozzle up to the engine bay from underneath the car. much better plan. might save your motor.