Performance of Multigrade Oils in Heavy-Duty Diesel and Gasoline Engines 670956

Results are presented showing that through judicious choice of additive and base stock components, multigrade heavy-duty oils can be formulated to match the performance of single-grade oils with regard to cleanliness and durability. However, there are a number of benefits inherent with multi-grade heavy-duty oils because of their viscosity-temperature characteristics. Foremost among these is the ability of SAE 20W/40 oils to provide the improved starting characteristics of an SAE 20W grade oil while maintaining the oil consumption control provided by an SAE 30 grade oil. To the operator, this means decreased manpower requirements for cold weather starting, decreased use of starting aids, increased unit availability, and longer battery and starter-motor life. Still another inherent benefit is improved fuel economy; gains range from essentially zero in warmed up line-haul operation to as much as about 10% in severe stop-and-go city operation where engines operate a significant percentage of the time at less than warmed up conditions.

The overall economics of heavy-duty multigrade oils vary from fleet to fleet, and can be evaluated only in the light of the particular operation. However, the increasing trend toward the use of such oils suggests that more and more operators are finding the economics to be favorable.