Stupid Question on Coolant Temperature

[Wayne's World]

So it is my understanding that on the 3.0 M54 motors, the thermostat is one with an electronically controlled 92F stat.

I've been monitoring my KTMP via the OBC on the dash and it runs at 86-87 consistently. Sometimes 89 if I'm going up a tall hill or just after a high speed run on the motorway.

So my question is, is this normal? Should I not be closer to 92? I did pour in a tad bit of RedLine water wetter almost 2 years ago and am slowly realizing that this is probably not the best in a daily driven car as lower temps may cause the engine to run a bit richer to reach the desired operating temp and thus burning more gas.

Is my logic sound here?