From CRC:
About the new EPA mandates concerning Diesel Fuel Additives, fuel and Model Year 2007 Diesel Engines that require Ultra Low Sulfur (ULSD):
In the short version additives are required to contain fewer than 15 ppm sulfur and be compatible with the new 2007 diesel engines and ultra-low sulfur diesel fuel. This EPA required labeling of existing product has been put in place to ensure that consumers do not add diesel fuel additives to model year 2007 and newer engines if those additives contain more than 15 ppm sulfur. These newer diesel engines have been designed to run on fuel and additives containing a maximum of 15 ppm sulfur. Of note, regardless of labeling all diesel fuel additives can be used in 2006 and older model year vehicles. All CRC diesel additives are compatible with the new 2007 diesel engines and the ultra-low sulfur diesel fuel. The only item, Bio-Con #05557 may not be used in 2007 or newer engines as it contains more than 15 ppm sulfur.
