a) It was a 6.5, not a Duramax

b) The test was over several years. The truck had 28,000 miles when I started. For the first two years or so I did not use an additive. Then I used Stanadyne for at least the next two years, winter, spring, summer and fall. I did not stop using it. Fuel came mostly from one station over the entire period. Routes and conditions were almost always the same. I recorded every drop of fuel and what type of driving. My mileage was consistent and repeatable. I got (IIRC) 5% better mileage with the additive; just enough to cover the cost of the additive.

c) If the additive was reducing or preventing deposits, so be it. The mechanism is immaterial; the results speak for themselves.

d) I feel it is easier to get meaningful results with one truck doing the same thing over the same routes with the same load day in and day out than with a fleet of trucks driven by different drivers and pulling different loads to varied destinations.

e) I am a trained scientist with a BS, an MS and even an Associate degree, and am familiar with the scientific method. I have confidence in my results.

QED