The Automotive Specialty Products Alliance has advised against using fuel additives not clearly identified as approved for use in 2007 trucks. The U.S. Environmental Protection Agency requires fuel additives sold after June 1, 2006 to be labeled.

Additives with sulfur content lower than 15 ppm should say on the label: “This diesel fuel additive complies with the federal low-sulfur content requirements for use in diesel motor vehicles and non-road engines.” Additives with a sulfur content higher than 15 ppm should say on the label: “This diesel fuel additive does not comply with federal ultra-low-sulfur content requirements for use in model year 2007 and newer diesel motor vehicles, for model year 2011 and newer diesel non-road equipment engines.”

Most additive makers didn’t know of this requirement before May 1, so many products on store shelves and in stockrooms are likely to be labeled incorrectly, the alliance said. The EPA requires the label to guard against the public using additives in 2007 engines that have too high a sulfur content; next year’s engines are meant to run on diesel fuel with only 15 ppm sulfur, and additives not meeting that requirement could damage the truck’s emissions controls.