JL,
I want one! I see how you did this, now all I need is a spare oil tank cap in case I screw up my original. (This will likely happen.) I've been thinking about making a temperature gauge for my SR for quite some time. One thing I worry about is the vibration affecting the guage. I'm thinking I could drill a very tiny hole in the back of the guage case and use a hypo needle to fill the case with mineral oil (water clear). Epoxy would cover the hole. Oil is the way guages are damped but I don't know what afect oil might have on the construction of a random guage. Like the face made of stiff paper instead of metal, or the painted numbers detaching due to the oil.
Tom