Fleet customers demand reduced operating costs. This necessitates the development of engine oils which can provide maximum fuel economy and extended oil drains, while still maintaining engine durability. This is particularly important in diesel engines produced since October 1998. These engines use retarded timing to meet EPA's emission requirements and, as a consequence in some cases, generate high soot levels in the engine oil.
Extended oil drains in 1995 Caterpillar 3406E and 1996 Detroit Diesel Series 60 engines found no statistical difference in fuel economy or wear between a synthetic SAE 5W-40 and an SAE 15W-40 using API Group II base stocks. Both oils had the same API CG-4/SJ quality level. Soot levels at oil drains of 40,000-50,000 miles (64,372 - 80,465 km) ranged from 0.5-1.2%.
Another study using 1999 Cummins N-14 engines found no statistical difference in fuel economy between a leading commercial synthetic SAE 5W-40 and a leading SAE 15W-40 using API Group II base stocks plus a premium additive system. Both had the same API CH-4/SJ/CES 20076/Mack EO-M Plus quality level. This finding is based on field tests, as well as TMC Type II/SAE J1321 fuel consumption tests conducted at Southwest Research Institute.
Based on used oil analysis from the 1999 Cummins N-14 field tests, a leading commercial synthetic SAE 5W-40 had statistically higher wear than a leading SAE 15W-40 using API Group II base stock plus a premium additive system. Both had the same API CH-4/SJ/CES 20076/Mack EO-M Plus quality level. These engines accumulated 230,000 miles (310,139 km) with 45,000-mile (72,405 km) oil drains, and averaged 4.7% soot at the oil drain.
In all lubricant “benchmarking” studies, the quality of the base stocks and the additive packages is critical to the final results. This study demonstrates that premium additive packages using API Group II base stocks at >99% saturate levels can equal synthetic oils in fuel economy and extended oil drain capability. This can reduce customer operating costs and provide significant savings, due to the lower cost of this engine oil.