AMSOIL Premium API CJ-4 15W-40 Synthetic Diesel Oil The premium choice diesel oil for model-year 2007 and newer heavy-duty and pickup truck diesel engines requiring API CJ-4 emission-quality oil standards. Delivers extraordinary lubrication in diesel engines in commercial, fleet and personal applications. Exceeds modern specs for emission-quality diesel oil. It withstands the stress of heat, soot and acids to help prevent deposits, wear and corrosion. AMSOIL Synthetic 15W-40 is wax-free with a broad viscosity range to provide exceptional cold-weather starting and high-temperature protection. It resists breakdown and offers maximum fuel efficiency over extended drain intervals.