my '01 is at 325,000 and was on the original thermostat. It was grunting to get to prob. 150*. I figured that it was stuck open, so last Sunday, I changed it out and changed the antifreeze. It's now getting up to regular temp, 180* - 190*. My milage was around 15.3 to 15.8. I think one time I got 16.3. I am running a Smarty set @ 9. I had taken a trip to Houston to see my son one weekend. I had set the Smarty to 0...... man that sucked. I didn't have any power at all ( ok, 0 is half power) but I figured that i'd get better milage at that setting. I got 17.3 . For the trip back, I set it back to 9, and got the same mileage. This was a year ago, when I went to get the dually rear axle for my build. Not a bad deal I think: rear end, 7 stock dually rims and tires ( 2 brand new) $700 , oh yeah, a new set of brake shoes too. Anyway. my mileage had been down since then. Now, since i've changed out the thermo, with the temps up, I should be getting better mpg's, right? ...... please post some pics of the set up with the resistors, or maybe a schematic drawing, so us plumbers can understand, please!!!!!!