Truck is running like a top. With the Rotella synthetic and warmer temps in the 20's with my Dura's aired down to 60psi, I just got 28.3mpg on the lie-o-meter on a 120 mile trip at 62mph. My lie-o-meter is consistently 18% high, so that would work out to 23.2 mpg on winter diesel.... Wow.

Anyway, the tach shows idle at 500 rpms. Sounds okay, and a bump on the high idle puts it right at 1000 rpms.

Reading the engine plate says 750 idle. Should I put a gauge on it?

 

if it's running fine, it could just the dash gauge. If you want to feel better, I would put a gauge on it.

 

Where does the gauge get its signal? Maybe I have to dust off a sensor....