I call it an issue, as its not a problem. Yet. 2005 LS 3.4L with 74 000 Miles/120 000 Kms (I'm in Canada). On the way back from a cross country trip, after getting gas and rolling out of the last town on the way home the temperature gauge inched higher. Since I got the car 5 years ago it would warm up to 3/8ths and stop. I never saw it go above that, dead of winter or hot hot Canadian summers on the highway at 75mph. Now it'll climb to the 1/2 point in traffic, even on cold days (32F/0C). If I'm moving it'll sit just above 3/8. Outside temp doesnt seem to matter, nor does running the heat or a/c in the car. Tested the dexcool, and it tested fine, but was chunky, so had it flushed. Also had the transmission and brake fluid done at the same time, but probably unrelated. Now it heats up slightly slower, but same results. I'd like to take care of this now before it gets worse or starts to cause damage. My next thought is to change out the thermostat, but I figured someone here may have a better idea.

 

I'm from Ontario and 1/2 gauge is okay gm's won't turn the cooling fans on til they hit about 210*F. The guage isn't 100% accurate anyway it's probably fine. But to make you feel better have a tech 2 scanner hooked up and watch a drive cycle warm up, and the thermostat can never hurt. I know running a cooler stat helps performance but in Canada it will be bad for the engine in the winter.