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Improving vehicle fuel economy is a major consideration for original equipment manufacturers (OEMs) and their technology suppliers worldwide as government legislation increasingly limits carbon dioxide emissions. At the same time that automotive OEMs have been driving toward lower viscosity axle oils to improve fuel economy, OEMs have worked to improved durability over an extended drain interval. These challenges have driven the use of API group III and/or API group IV base oils in most factory fill axle oils. This paper details the development of a novel lower viscosity SAE 75W-85 axle technology based on group II base oil that rivals the performance of a PAO-based axle oil and challenges the conventional wisdom of not using group II base oils in fuel efficient axle oils.

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.