if possible check with an infrared gun (pointer type thingy) that is the most accurate way.
and if you don't consume too much fuel, it is probally the gauge that is off.

it also really depends where you meassure, my sender has been placed in two different locations with different result and now it has been in the oilfiltertop. but even that wasn't stable as there was a difference between the bracket mounted to the shroud (type3 engine), with a bracket on the exhaust flange (way hotter) and now on the stabilisation bar.
so there are many variables and i personally think you should 'know' your gauge and go from there to know what is too hot and what not. i think oilpressure is a better factor to hold your eye on.