It might work ok for the gas gauge. As mentioned, the gas gauges will work on 12v. The thing about that is nobody knows the long term effect. I understand some people have used their gauges on 12v for many years, but for how many hours? Based on what I discovered, I'm almost certain the little metal piece will in time become so over-magnetized it will never again work on anything but 12v. Which might be ok. But the flip side to that is the magnetic coils may in time be affected, also. It will take a long time, but the effect will be irreversible.
The real key with voltage reduction is to think of it as voltage destruction. And when you destroy electricity, the unwanted/unneeded portion becomes heat. With the resistor, often the heat ranges from objectionable to dangerous. But not with the gas gauge. It doesn't use enough juice to be a problem. Personally I don't like this method, however that's probably just me. Soon...very soon...I'll be finished testing a handy adjustable voltage reducer I've made. More to follow...
