Well, my car that ran at halfway almost all the time on the stock gauge is a different story with a mechanical ultra-lite. The car now runs 180-205 depending on operating condition, AC on or off, and outside temps. I wouldn't base ANYTHING on what the stock gauge says, really.
yep, the stock gauge is about as useful as an idiot light (perhaps less useful, as it can impart a false sense of security). i would not dream of tryin to interpolate its reading.
get a real temp and oil pressure gauge and know what is goin on, IMHO.