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
The Constitution needs to be re-read, not re-written!
If you can't handle Dr. Seuss, how will you handle real life?
Current oil burners: MB GLK250 BlueTEC, John Deere X758
New ride: MB GLS450 - most stately
Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510