Effects of dumbbell blending of light and heavy hydrocracked base oils on the performance of automatic transmission fluids

Abstract

Over the past two decades, the performance requirements for automatic transmission fluids (ATFs) have undergone a significant number of changes in response to mandated legislation by government and regulatory bodies to improve the air quality through reduced emissions while providing energy efficiency and 'fill-for-life capabilities. In order to formulate a high-performance ATF, it is now necessary to complement a strong and well-balanced additive package with a selection of high-quality base oils. This study will investigate the effects of several base oil properties on ATF performance. This will include a comparison of formulations blended from straight-cut base oils with those produced by blending light and heavy viscosity base oils from the same slate but to the same base oil kinematic viscosity. Five commercially available base oils with a kinematic viscosity range of 2 to 8 mm(2)/s at 100 degrees C form the basis for this work that in turn were used to formulate four different ATFs at the Hyundai Diamond SP-3 performance level. The base oils were produced from the iso-dewaxing of a hydrocracker bottoms feed. The finished oil testing included viscometrics, seat compatibility, oxidation stability, and frictional behavior. The benefits and limitations of using dumbbell blending on the properties of base oils and the performance of automatic transmission fluids are described.