On June 1, 2006, the Ultra Low Sulfur Diesel Fuel (ULSD) regulation went into effect. This regulation, mandated by the EPA, was created to reduce emissions in 2007 or newer model diesel vehicles by lowering the sulfur content of diesel fuel to less than 15 parts per million. This regulation requires that ALL diesel fuel additive products must be labeled or stickered stating whether the product complies with the new ULSD regulations (contains less than 15 ppm sulfur), or does not comply (contains more than 15 ppm sulfur). Because the stickered DieselPower!® brand products contained more than 15 ppm sulfur, they are required to have the does not comply sticker. However they are totally safe to use in ALL 2006 and older model diesel engines.