Multimeters for diagnosing car problems

A £5 DT-830 style meter is all you need for 99% of everything you need on a car, here's an article explaining why they're actually great:

https://hackaday.com/2020/09/24/in-praise-of-the-dt830-the-phenomenal-instrument-you-probably-dont-recognise-for-what-it-is/

Ideally one with a continuity buzzer as that's one of the most useful features in fault-finding.

And I'll let Big Clive explain how to use a multimeter without blowing it up:

https://www.youtube.com/watch?v=-QDW0LRQVrY