Chevrolet Repair: CK engine light, radiator cap, high mileage

Question
Robert,
I have a 2003 Trailblazer with a 6 cylinder Vortex engine. The check engine light comes on for days at a time then goes out for days at a time.  I stopped at a local parts store that offers free testing and they said the code read low engine temperature.  My temp gage reads around 170 degrees consistently, so the thermostat seems to be working?Runs fine all the time.  Any ideas.....thanks!

Answer
Your engine should be running around 195 degrees. Newer vehicles require hotter temperatures than older vehicles to provide better emissions and gas mileage. I feel 170 degrees is too low if that's as hot as the engine gets. I would replace the thermostat and depending on the mileage change the coolant and radiator cap also. If you have over 50k it wouldn't hurt to do that. I personally do not agree with the long coolant change intervals that GM recommends. Just about every one, it has corrosion at the high mileage. Make sure you use a mix of 50/50 Dexcool and distilled water or just buy the premixed which is better.

I would do this before going further with the check engine light...most likely this will fix the problem and you should improve on gas mileage with engine running hotter.