I drive a 2002 Saturn SL2 and I’ve noticed a bit of an odd condition with it; the running coolant temps seem very low. By “running” I mean fully up to temp, ‘normal’ operating conditions. I can’t help but wonder if it’s costing me mpg’s, although the car really gets excellent mileage seemingly ‘in spite of’ the odd coolant temps.
Here’s what I mean:
A week or 2 ago I decided to hook up my scanner and monitor a few things to try and track down a high idle speed issue that’s recently popped up. What I found is that at full operating temps my car was running between 154-158deg ECT. Seeing this I decided to go ahead and change the coolant temp sensor since S-series cars are known for crappy temp sensors and a new was is only $9 (man I love how cheap parts for this car are!
). I figured it had to be reading incorrectly. No dice, the temps are exactly the same, to the degree, with the new sensor. It shows none of the classic signs of a stuck T-Stat either; the car warms up fast (faster than any other car I own actually) and the engine temps are rock solid stable in freezing cold or blazing heat. The gauge has read exactly the same since I bought the car a couple years ago, I just never monitored it until now.
The thing is, I consistently get 40-41mpg in warmer weather and it’s been 37-39 since winter set in. Those are very good numbers from a ‘twin cam’ Saturn so it’s hard for me to believe that the coolant temps are costing me much. However, the logical side of my brain keeps telling me that those temps are too low for optimal mpg’s.
Anybody ever seen such low, but totally stable, operating temps?