Doc's Diesel 15W-40 Full Synthetic Heavy-Duty Diesel Oil 55 Gallon DrumDoc's Diesel Engine Oil: Doc's Diesel 15W 40 Full Synthetic Heavy Duty Diesel Oil is specially engineered for todays hard working diesel engines whether you're running a new emissions compliant rig or keeping an older workhorse in the game. Engineered for excellent wear protection, our oil thrives in severe operating conditions, ensuring that your engine stays protected under the toughest circumstances. With strong oxidation and viscosity control, it