[Ptero]

The question was what are the three most useful gauges. You need a gauge to verify that you need to replace your 7-year-old battery? I use a load tester for that but I keep it in my tool box.

Also, the bird is not a yaw string. It conveys a lot more useful information.

I used to be gauge-happy. I had so many gauges on my XJ12 that I had to buy a dual-needle exhaust temp gauge because I ran out of holes. I'm a big fan of large tachometers and a fanatic for big pyrometers on big diesel engines. But those are all for performance applications. For economy purposes, if I were going to give you just one of all I've used over the years, I'd give you the bird. The bird rocks!