Okay, now I'm impressed. I'll admit to being a skeptic, especially when it comes to mileage numbers. It's so easy to get good numbers on one tankful and shout about it. But then the next tank comes out not so good and you have to average them. All about filling...how much is full?

For this test, I fill til clear diesel (no foam) sits at the vent tube. Won't take any more. The driving conditions remained the same -- namely 50-60mph on icy, snow-covered roads. At least 240 miles in 4WD up and down in the mountains, often pushing 3-4 inches of show, winter #2 fuel. Same pump, both tanks.

In Part I, this truck got 18.03mpg over 542 miles factored to 529 miles (tire size) and hand calculated. The OHC reading of 18.9 was also factored to 18.4 because of tire size. Once the Smarty arrived, we corrected the tire size until we have *exact* match between GPS and speedo.

With the gauges installed, I've been driving by EGT, meaning light throttle to keep it under 700F. Won't go up the hill? Shift down to 5th. With one exception (the mile long 7% grade), that's how I drove both tankfuls. Did I mention this was a MAX mileage test? In a way, I'm glad this test is over, because now I want to see what +40hp really means.

So... the numbers. The OHC kept climbing throughout this test, hitting 20.0mpg today while driving the last 45-50 miles before filling the tank. We've all read how tuners can skew the OHC, so this number wasn't all that compelling. But, the trip odometer had passed 420 miles before the fuel gauge passed the half-full hash mark...and that was encouraging. My truck seldom gets past 360 miles on the top half of the tank.

To the pump then. 506.8miles on the now calibrated trip odometer. The pump clicked off at 20.6gal...and I was able to trickle in a few more for 24.30 gal when clear diesel fuel was level with the vent tube.

20.86mpg Hand Calculated. Net gain of 2.83mpg.

 

That's fantastic....Nice numbers

 

I also had a gain of 2.13 mpg and I didn't go nearly as easy on mine as you did on yours, so let your foot live a little The mileage tune is awesome. Nice test man thanks for keeping us informed, I was wondering when you were goin report back in, since I read "max mileage effort part 1"