I'm assuming its the thermostat but i'm still running the hydraulic fan. I've only had my car for a few weeks now and the most i've driven it was for probably 30 mins, but it was about 50 degrees outside.

 

Mine never fluctuates no matter how hot or cold it gets.

 

The only time mime moves is when I go around a sharp curve or exit ramp. OLT says it does it all the time, its when you change out to brighter needles that you REALLY start noticing the movement. My gas gauge also does the same thing. They both move right back when I go straight again. Just my experience.

 

On my last 95 sc4 always dead center. On my 99 sc3 right now stays slightly above center all the time even driving through the 112 degree weather in Vegas blasting cold ac !

 

mine is always like luxor's or a tad bit below. it never goes higher than that though. most of the time though it is lower.

 

Almost all modern cars (last ~25 years) in the US have extreme damping on temp gauges, so all they really tell you is "cold" "normal" "hot".