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Public concern and increasing regulations surrounding environmental issues, such as CO₂ emissions, are making it important for car makers to improve the fuel efficiency of the vehicles they manufacture and sell. A wide array of transmission technologies are being employed towards this end including, but not limited to, 6, 7, and 8 speeds stepped automatic transmissions, dual clutch transmissions (DCT) and continuously variable transmissions (CVT). The number of passenger cars equipped with CVTs has been increasing and push belt CVT types (b-CVT) are widely used. Since engine torque is transferred to the wheels via friction between the steel elements of the belt and the steel pulleys in a b-CVT, having a high metal on metal friction is required. As the CVT fluid is a key part of the CVT system, using a special CVT Fluid (CVTF) is critical in order to provide and maintain the required high metal-on-metal friction performance.

Global original equipment manufacturers (OEMs) have requested lower viscosity automatic transmission fluid (ATF) for use in conventional and 6-speed automatic transmissions (AT) to meet growing demands for improved fuel economy. While lower-viscosity ATF may provide better fuel economy by reducing churning losses, other key performance attributes must be considered when formulating lower viscosity ATF(1,2). Gear and bearing performance can be key concerns with lower-viscosity ATFs due to reduced film thickness at the surfaces. Long-term anti-shudder performance is also needed to enable the aggressive use of controlled slip torque converter clutches that permit better fuel economy. And, friction characteristics need to be improved for higher clutch holding capacity and good clutch engagement performance. This paper covers the development of next-generation, low-viscosity ATF technology, which provides optimum fuel economy along with wear and friction durability.