I have a 2005 Relay, 6 cylinders. Recently the engine temp gauge is fluctuating between the center line and ¾ line. I am also due for an oil change and am down 1 quart.
Does anyone know if this fluctuation is normal due to the low oil level, or if this is just the precursor to a more serious cooling system issue?

 

Well, centerline is about normal (please note, I said "about" - gauges and sensors do differ a bit), and 3/4 would be where the cooling fan would kick in if I was idling somewhere, or stuck in traffic. Personally, I'd have the oil change done, and watch the gauge for a bit before making any snap decisions

 

Thanks for the feedback OceanArcher. My experience so far (I bought used thru a dealership), calibration issues aside, is that the gauge remains pretty steady at the center line, about ±3% fullrange. The cooling fan would run in if the gauge traveled only about 20% between center and the ¾ line.

This morning, I did get the oil & filter changed and refilled with Syntec. Indication has returned to normal and is steady as before.

I am amazed that being down only 1 quart of oil can make that much of a difference; the indication on the dipstick had just reached the lowest hash mark. Clearly the engine designers did not leave any margin when designing this system which is almost unbelievable to me. Every other engine design I have looked at has an operating margin to act as a buffer.

Anyway. I’ll post again if something further develops. Thanks again for the prompt advise.
Best regards.

 

Lotta people don't realize that engine oil helps remove heat too. Glad you are back on the road, but I'd keep a cautious eye on it for a while. Also, I'm suprised at your oil loss in a 6-cyl. The early single-cam 4's were notorious about it, but I've not heard a lot about the 6's being that way too

 

So glad I came across this post because my vehicle was having the same temperature fluctuation issue. At least I know what could possibly be the problem. We'll see.