[TDIwyse]

Originally Posted by Pierre Louis

Don't be. Additives don't improve mileage. You'd have to do a study to actually show it anyway. Your car may be cycling through its DPF or something else like your driving style changes.

http://www.akenergyauthority.org/PDF...0Additives.pdf

Well, saying "additives don't improve mileage" is too broad. Here's a study done by SwRI...

http://www.swri.org/

"Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is one of the oldest and largest independent, nonprofit, applied research and development organizations in the United States."

...showing an example of an additive that does. Study paper shown in link below.

http://greenmyfleet.com/index.php?op...ves&Itemid=119

They followed SAE J1321 protocols with straight D2 and then repeated with the test additive in the same fuel. Average fuel efficiency improvement was just over 3%.

So ... some additives can and will improve efficiency.