ok if you've only ran it that much you really shouldnt see a difference once you run it more you probably will but if you have no leak and your not overheating your fine it's ok to have the gauge fluctuate mine does it and everyone elses i know but as long as theres no over heating your good

 

if you get good heat and its not overheating it'll be fine. you could put a mecanical gauge in it to see what its really doing. mechanicals are the most reliable in my book.

 

My gage has never fluctuated so I'm not sure why others think that would be normal. Might want to look at the temp sensor next. Those have been known to fail, and X2 on getting a mechanical gage to make sure everything is kosher.

 

I thought that was what thermostats do..the temperature builds until it hits the opening point of the thermostat(195 for mine) then it opens and the temp drops and the cycle repeats. Mine has been doing that for years. If it rises and then drops and doesn't come back up I'd say you have a faulty thermostat.

 

when it says 195 it means your temp should stay at that temp it opens and closes to keep the temp at 195

 

Throw the old thermostat in a pot of boiling water and watch if it opens up all the way...

 

I don't know if this has anything to do with this problem what so ever, but I have also been having this problems for the last week or so.
Nothing fixed it. By a fluke I pulled my PCV valve, and it was all gummed up and stuck. I cleaned it out with some brake cleaner and ran som air through it with my compressor. Last I flushed it with some wd40 and the rattle came back. The first thing I noticed was that my engine temp was up to normal again and after a little run my engine started to operate like normal again to. I would not know how a PCV valve would keep the engine from gettin up to temp, but it clearly can.

 

Did you fix your problem?

 

i got the same year jimmy and mine does the same thing i top it off with coolant and it goes back to normal and the heat starts working again