Higher Quality Base Oils for Tomorrow's Engine Oil Performance Categories

Paper #:
  • 982582

  • 1998-10-19
Henderson, H., Mack, P., Steckle, W., and Swinney, B., "Higher Quality Base Oils for Tomorrow's Engine Oil Performance Categories," SAE Technical Paper 982582, 1998, https://doi.org/10.4271/982582.
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.Although improvements in low temperature fluidity are not expected to be limiting for tomorrow's automotive engine oils, the selection of dewaxing operation still plays an important role. For example, low temperature viscosity is improved through hydro-catalytic versus solvent dewaxing. This is tied to the type and amount of residual wax in the base oil.Engine performance is affected by base oil composition. Higher saturates base oils are beneficial with the new API CH-4 (PC-7) HDEO lubricants. Oxidation and engine performance benefits, in sludge and deposit control, of higher saturates base oils are key to achieving the ILSAC GF-3 performance limits.The impact of base oil composition on PCEO and HDEO performance is discussed in terms of several engine oil properties. These include volatility, shear stability, low temperature fluidity and engine performance. This will focus on future North American and current European engine oil qualities and the shift to higher quality API Group II+ and Group III base oils.
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