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Due to its simplicity and fuel economy benefit, continuously variable transmission (CVT) technology has gained a lot of attention in recent years. Market penetration of CVT technology is increasing rapidly compared to step-type automatic transmission technology. OEMs, Tier 1 suppliers, and lubricant suppliers are working to further improve the fuel economy benefit of CVTs. As a lubricant supplier, we want to understand the effects of fluid properties on CVT fuel economy (FE). We have formulated fluids that had KV100 ranges from 2-4 cSt to 7-9 cSt with various types and viscosities of base oils. Wide ranges of viscosity indexes, steel-on-steel friction, and other properties were tested. Full vehicle fuel economy tests were performed in a temperature controlled environment with a robotic driver. The test revealed that there was more than 3% overall FE variation compared to a reference fluid.

This report focuses on an extended investigation of the durability of Dual Clutch Transmission (DCT) fluids. The performance requirements of DCT fluids differ from those of traditional step automatic transmission fluids. For that reason, key performance lab tests are discussed in this paper. Friction durability is measured with a modified version of the JASO M348 SAE#2 friction plate test. In addition, results from a vehicle chassis dynamometer test are discussed. This test involves running a 2008 Volkswagen GTI for 60,000 dynamometer miles (42,000 cycles) of severe acceleration and high speed conditions. Finally, a new DCT fluid, which performs well in these tests, offers friction stability and superior wear protection of transmission hardware, when compared to the commercial reference fluid.

This paper reports its findings in three separate parts. First, a comparative study is made among existing commercial dual clutch automatic transmission fluids (DCTFs). Significant differences in fluid torque capacity, friction material compatibility and copper corrosion performance were found among the fluids. Second, both a new vehicle chassis dynamometer durability test and a SAE#2 durability procedure are offered, specifically designed for DCTs. A 2008 VW GTI did well in the severe 60,000 mile chassis dynamometer procedure. Third, a new DCT fluid is discussed.