So I was driving home from work today and noticed my engine temp needle was slowly fluctuating between 3/4 and 1/2 of the way up. Of course this is technically well within the "normal" range, but I've owned this truck for 12 years (bought it new in 96) and I've never once seen it go up that high. It usually stays between 1/4 and 1/2 at the most when I really push it. I did have the A/C running today, but that is normal, and it was only about 85 degrees outside. During mid-summer around here it can get over 105 outside and I've still never seen my temp gauge go up that much even running the A/C full blast for a long period of time.

I wasn't driving abnormally and wasn't stopping a lot (I know the A/C can make the engine hot if you're not moving), just the normal drive home like any other day.

Any thoughts? Is this a sign that my thermostat is going out? It obviously isn't stuck closed because the engine temp did fluctuate, so I'm assuming it was opening and closing somewhat.