Formulating Automatic Transmission Fluids with Improved Low Temperature Fluidity

The driving force for reducing the low-temperature viscosity of automatic transmission fluids is improving low temperature transmission operability. The need for this change in fluid performance can be attributed to the evolution from hydraulic control of transmissions to electronic control. This new requirement for automatic transmission fluids of improved low temperature fluidity causes a shift in the viscosity of the base oil used to blend the fluid. Conventional mineral oils are still acceptable bases for these new fluids as well as specially refined mineral oils and synthetics. The shift in fluid rheology and base oils also impacts oxidation resistance, foaming characteristics, anti-wear performance in hydrodynamic regimes and fluid flash point. All of these potential problems can be overcome by the correct choice of base fluids and additives.