There is only one answer to that question:
When a fire erupts in your Miata you will have an opportunity to extinguish and save your car. (That is the one answer.)
Here is what you need to consider when purchasing a fire extinguisher:
- What size: It should be at least a two and a half pound unit. I prefer a five pound but space could be an issue.
- What agent: I like an ABC dry chemical. However, it leaves a dust type residue. The agent that does not leave a residue is called Halotron, a clean agent. If you will recall the term Halon; Halotron has replaced Halon.
- Painted or Chrome shell: A classic or Miata would host a nice chrome unit, however, cost is a factor.
- Quality of unit: I would select an industrial unit. It has metal handles and a better mounting bracket, to mention just two reasons.
- Mounting bracket: The industrial unit has a MUCH stronger bracket to hold the unit.
Now that you have an idea of the type of extinguisher you might consider, you must know how to use it on a fire. A car fire in the engine area could be very difficult to extinguish. A fire there tends to move under the engine and to the other side of the engine compartment. You could end up chasing it around.
Bottom line, I recommend not only having a fire extinguisher in your Miata but also buying the best you can find and then know how to use it correctly.