I'm not sure where to look first on this - up to now, my engine seemed to have been running a little above 175 (my gauge is in °F, but that is about 80°C), maybe 190° (87°C). It is hard to tell because it is only labled at 175 and 250, with one unlabeled mark in between - 200°? 225°?

Yesterday on my drive home, I noticed that the temp had jumped up to somewhere between 175 and the unlabeled mark - noticeably higher than it has been for the last week that I have been driving. It seemed to jump around a little bit - quickly, probably something strange with the sensor...

I thought it was just something with the sensor, BUT it continued to stay up there and wouldn't come down, so I turned on the heat for about 1-2minutes. It dropped down then pretty quickly to 175 and hovered around that the rest of the way home - another 10 minutes or so of freeway driving, even after I had turned the heat off.

Today on the way to work, the same thing happened - running a little hot, I turned on the heat, and it dropped down again and stayed there for the rest of the drive even after I turned off the heat.

Is this indicative of air in the cooling system? Looking through a search that is what it seemed like it could be, but I am not sure. Also not sure what to do about that if that is the case.

This isn't my instrument cluster, but it is a pic of the temp gauge for reference:

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