Better Gas Mileage!

[gibbons948]

i bought my 03 GMC 2500HD about 2 months ago and always got about 11.5 mpg and it ran at 170 deg. F. i thought this was normal opperating temp until i got a check engine light with a t-stat code. i replaced the t-stat 2 days ago and now im getting 14.5 mpg and runs at a constant 200deg F. who knew??...that will help the wallet this winter!

[Lincoln30]

Maybe an expert can chime in here but I assume that at 170 you were in "open loop" all the time and that was what was effecting mileage, et al.

[gibbons948]

yeah, thats what im thinking. at times it would run at 200 but not for long. just never noticed it because thats how it was when i bought it.

[xsports33]

If your engine is reading colder temps it will dump more fuel because it thinks it's getting a colder denser charge of air. This is the problem a lot of people run into when they modify to a colder T-stat, like 160, and don't get a tune. They run pig rich and MPG goes to hell without a tune.