Ok guys, here it is.

I had a previous thread on Diesel Kleen. So that everyone has access to this mpg info, I want to post the reply I got from DK about the extra mpg they claim. It's an "up to 8%", and someone said well, 0% gain is part of "up to". But the bottom line is, sounds like they have a fair claim at about 5% gain by using it. Here's their reply to me.......

Cetane is a very powerful energy compound that helps the fuel to ignite
a split second sooner which helps the fuel burn more completely, reduces
engine knock and helps reduce emissions.

The Department of Energy, Clean Cities Tennessee and Wal Mart
Transportation all conducted their own testing using their own equipment
and test set up and they found that fuel economy did improve, usually
around 5% for mix fleets or vehicles, that emissions went down and the
vehicles had better performance. Clean Cities TN also ran NOx emissions
and found that Diesel Kleen reduce NOx by 9% (running) to 28% (idle).
Total Fina did a study with new injectors and found that when using a
strong detergent and strong Cetane Boost fuel economy increased 2%.

.....Jeff 1991 300d, 111k