Heavy-duty engines need heavy-duty engine oil, nothing works better than our Speed Turbo 15W-40 Heavy Duty Diesel Engine Oil. Whether you have a heavy-duty truck or any car, our oil provides the performance and protection that fit your needs. Our oil is a fully synthetic, high-performance diesel engine oil that gives long drain capability & fuel economy potential for modern diesel engines. Speed Turbo 15W-40 Heavy Duty Diesel Engine Oil is formulated to give exceptional performance in newer engine designs.