Originally Posted by Jethro_3

The aeroforce gauge tells a different story than the factory gauge. I can hear the fans and watch the aero gauge as the fans turn on and off to the degree. My engine never get belows 173* with the 160* stat. But now with the 160* stat I do not see the 230* idle I did with the factory stat. Now at idle the highest temp I see is 190* and then the fans turn on high and get the temp to 175* in a matter of a minute(s).....

I have a hard time believing that tuning the truck to run 10* cooler would affect the mpg that much. I am not saying that I have the answer but I would like to hear if your driving habits are EXACTLY the same since you have the tune. I do know that when the temp on the engine and intake air temp go up the engine will retard the timing since the incoming air can not hold as much fuel causing detonation. I do agree that most engines do not run as good with 160* as 175*. Just because you have a 160* thermostat does not mean the engine will always be at 160*, it only keeps the engine temp above the thermostat temp. Even on the days it was below 32* in Austin I naver saw the temp go below 173* after I warmed the truck up. Just my opinion, hope it helps.