Marvel Mystery Oil should not be used in your 2007 Chevy Dura Max Diesel. The 2007 diesel engines were designed to operate on Ultra Low Sulfur Diesel (15 parts per million (ppm) of sulfer or less). The reason Marvel Mystery Oil should not be used is not because of high ash content, but rather at the recommended treat rate, Marvel Mystery Oil would raise the sulfur content of the fuel by 1.6 ppm sulfur. Thus, you could be raising the sulfur content of the diesel fuel to 16.6 ppm sulfur which is outside the limit set by the diesel engine manufacturers. This higher level of sulfur could potentially impact your warantee.
