Developing Next Generation Axle Fluids – Part II - Systematic Formulating Approach 2002-01-1692
Light trucks and sport utility vehicles (SUVs) have become extremely popular in the United States in recent years, but this shift to larger passenger vehicles has placed new demands upon the gear lubricant. The key challenge facing vehicle manufacturers in North America is meeting government-mandated fuel economy requirements while maintaining the durability required for severe service. In light truck/SUV applications, gear oils must provide operating temperature control under extreme conditions such as trailer-towing. Higher operating temperatures for prolonged periods can adversely affect metallurgical properties and reduce fluid film thickness, both of which can lead to premature equipment failures. In our view, operating temperature is an important indicator of durability. Unfortunately, lubricants optimized for temperature control do not always provide the best fuel economy. Our objective was to design lubricants which improve operating temperature properties while retaining a high level of fuel efficiency.
Part I in this series, “Test Methodology to Measure Durability and Temperature Reduction Properties of Axle Gear Oils” (SAE 2002-01-1691), describes a full-scale axle test which simulates a variety of vehicle operating conditions. The current paper outlines a systematic formulating approach which utilizes this tool to develop durable axle lubricants which are compatible with current fuel economy requirements.