I also had one of those crap red harbor freight meters, and really found that it was basically useless. One day at work we decided to set it on the bench and hook it up to the 75kv hipot to see where it would flashover... I think ours met it's demise at around 1kv which surprised me (I thought it would be lower)... The funny part was instead of stopping we just kept turning it up more till it arced again! Keep in mind we were standing 10 feet + away at the time doing this from a shielded control panel.
I feel pretty safe using even a crap meter like this on a car, heck if your not good with this meter, then just get a good old automotive test light and that will do almost everything you need unless you are troubleshooting fuel injection stuff or something.
I will say, I have also had a bad experience with a car battery and a CB radio... Where the battery became shorted through the radio and the fuse installed was not small enough! The PVC insulation melted off the RG-8x coax and filled the cab of the vehicle with toxic fumes to where I could not see! It finally burned the coax in two after about 30 seconds along with melting a trace in my carpet! The main line fuse (dont remember value) never blew! When stuff does go wrong, it can really suck! If I had been driving rather than working on my vehicle in a parking lot I might have run off the road from not being able to see...
This is exactly why I get worried every time I hear one of these kids with the big stereo systems telling me that he has a two Farad cap on his wiring to his Amps... I hope that thing is in the trunk in an enclosure so it never gets a penny that fell through the seats and shorts one of the terminals to the frame of the seat or something...that could really suck! By the time most slow blow automotive fuses cut the circuit the carpet might already be on fire!
I actually have met two people personally that have had jewelry they were wearing short across a high energy circuit and neither one of them will do that again! One guy had his wedding ring get shorted across a car battery while tightening the terminal clamps with a wrench and it burnt a circle on his ring finger where it cauterized the skin! Now he does not need the ring cause it's branded into his finger permently... The other was a girl I went to school with that leaned over a HV transformer in a lab (which she thought was not energized) and it arced to her gold necklace which was hanging down from her neck! She was in a coma for 3 weeks, had to relearn how to walk and talk again and had a piece of her foot the size of a quarter blown out the side where the arc went to ground.
Guess the order of the day is better safe than sorry!
Now if you want to blow something up on purpose that's a different story
just don't make an ass out of yourself on YouTube by getting lye or battery acid all over your face screwing around like an idiot,like the kids making these chemical bombs for fun.
Do it as a controlled experiment from a safe distance, and whatever you do, Don't do it to your wife's car! Then you really might get hurt