Cooling question (overcooling?)

My closed cooling system seems to work well, I replaced the fluid reservoir and a few hoses earlier this year, and havn't had any problems with it since.

During the summer, it would get up to operating temp (around 210 degrees) regularly and would cool itself properly, but now that the cooler tempuratures are here it is not getting past around 150 degrees unless I'm climbing a really big hill or some extended 4wheeling. It seems that it's staying a bit too cool right now. Is this normal? Last winter it did the same thing but I never checked into it. My gas mileage has dropped a little since the cooler temps started, making me wonder if the t-stat isn't faulty or something.

That's what I would first check. Sounds like it may be stuck open.

You should be able to watch the temp rise from cold to about 210, then drop back down a bit as the stat opens, then stabilize at operating temp. I suspect a stuck open stat.

okay thanks, I'll replace it tommorow. 195* t-stat what I need?

I have one doing the same thing, goes up to 210 and drops back to between 100 and 210. It's probably the wrong tstat the PO put in or it's just not working right. Was going to do it today and while I had 3 new oem tstats in the tool box not a gasket to be found. Trip to dealer tomorrow.