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The continuing evolution of higher performing automotive lubricants has led to significant changes in the qualities of base oils which form the building blocks for these products. Through the use of hydroprocessing and hydrodewaxing technologies, the growth of API Group III fluids has been dramatic and in many cases can deliver performance previously reserved to polyalphaolefins (PAO's). This paper will review the benefits that can be obtained from these new API Group III fluids with particular emphasis on severely hydrocracked and hydro-isomerized processing. Examples will be provided from automotive products where the direct replacement of API Group IV PAO's with API Group III fluids can maintain and in some instances improve “synthetic” performance.

Changes in the performance requirements of passenger car (PCEO) and heavy duty (HDEO) engine oils are dra-matically impacting the design of tomorrow's automotive lubricants. Specifically, lubricant base oils are shifting toward higher quality API Group II+ (100 - 120 VI) and Group III versus more traditional API Group I and Group II. A feature of premium base oils is high Viscosity Index (VI). Since base oil VI is linked to volatility at a particular kinematic viscosity (KV), higher VI reduces base oil and finished oil volatility. This is key for ILSAC GF-3 PCEO requirements where significant volatility reduction is required to reduce oil consumption. High base oil VI also allows for higher base oil KV and reduced viscosity modifier (VM) treat which improves shear stability of finished fluid. This also provides opportunities to formulate PCEO against the European engine oil requirements where volatility and shear stability are key performance requirements.

Significant changes are occurring in the development of automatic transmission fluids (ATF) which impact the selection of both additive components and lubricant base oils. In particular, the need for improved viscometrics at high and low temperatures, combined with the need for increased oxidation performance and shear stability are moving formulators towards use of higher quality API Group II (100 - 120 VI) and/or Group III base oils. Several benefits are apparent with the use of API Group III base oils in ATF. Their naturally high Viscosity Index of >120 provides opportunities to use a higher base oil viscosity compared to API Group I and in many instances Group II base oils. This reduces the amount of Viscosity Modifier in the finished ATF and improves overall shear stability. Higher kinematic viscosity also improves volatility which leads to improved oxidation resistance. Low temperature fluidity can be improved by modifying the amount and type of residual wax in the base oil.

The results of numerous laboratory bench tests and over-the-road field tests conducted on fluids blended with base stocks of varying physical properties are compared. The effects of using oils derived from solvent-refining versus those manufactured from a hydrotreating process are examined. Other areas investigated include comparisons of high vs. low VI; light vs. medium grade neutrals; and additive response to these differing base s tocks. Although high viscosity index (HVI), hydro treated, medium grade neutrals generally gave superior results in the tests performed, it was determined ATF's blended with light grade hydrotreated neutrals of low viscosity index (LVI) also showed promising results when evaluated against standard industry tests.

A line of high quality multigrade diesel engine oils suitable for long drain applications has been developed using hydrotreated basestock. Laboratory and engine dynamometer tests indicated that lubricating oils using hydrotreated basestock have superior control of diesel piston deposits and oxidative viscosity increase. Excellent performance of multigrade diesel engine oils using both hydrotreated and solvent refined basestock over extended oil change intervals has been demonstrated in extensive field trials. Cold weather benefits for multigrade diesel engine oils were defined by cold room studies and outdoor trials.