Almost impossible to tell, since the gauge senders vary a lot, as does each gauge.
The best way to tell what the heck is going on is to get a dip stick thermometer (or borrow one from a friend), stick it down the dipstick tube and see what it says. Doing that, you can "calibrate" your electric gauge with simple magic marker lines on the face.
You want it to be under 210F when on a turnpike, and under 200F-sih around town.
The dipstick thermometer a lot of us use is from http://www.mainelycustombydesign.com/engine_components.html#dipstick