Low-Temperature Rheology of Multigrade Engine Oils - Formulary Effects 831716
Several major U.S. engine manufacturers recently revised their factory-fill and service-fill engine oil specifications after experiencing a number of engine failures related to low-temperature oil pumpability. Changes include lower limits on ASTM D97 pour point and adoption of stable pour point requirements as measured under cyclic low-temperature conditions. Factors such as base stock, VI improver, pour point depressant and detergent-inhibitor package selection can have a pronounced effect on a fully formulated engine oil's low-temperature flow properties. It has been found that by a judicious combination of HVI and MVI base stocks, one can formulate multigrade engine oils with excellent low-temperature flow properties. Properly formulated oils can readily meet all of the current factory-fill and service-fill specifications, and are expected to minimize the possibility of any future low-temperature oil pump-ability related field problems.