Breaking the Viscosity Paradigm: Formulating Approaches for Optimizing Efficiency and Vehicle Life

The popularity of light trucks and sport utility vehicles (SUVs), coupled with growing consumer demand for vehicles with more size, weight and horsepower, has challenged the original equipment manufacturers' (OEM) ability to meet the Corporate Average Fuel Economy (CAFE) specifications due to the increased contribution of these vehicle classes on fleet averages. The need for improved fuel economy is also a global issue due to the relationship of reduced fuel consumption to reduced CO₂ emissions. Vehicle manufacturers are challenged to match the proper fluid with the application to provide the required durability protection while maximizing fuel efficiency.

Recent new viscosity classifications outlined under SAE J306 aid in more tightly defining options for lubricant choice for a given application. Changes to the SAE J306 viscosity classification define new intermediate viscosity grades, SAE 110 and SAE 190.

This paper will describe the use of controlled laboratory testing methods for the development of axle fluids that maximize both the fuel efficiency and durability performance across the wide spectrum of these new proposed viscosity classifications. The relationship of viscosity and fluid formulation choices will be examined with respect to inherent fluid properties, as well as the impact of these fluid properties on axle efficiency and temperature performance characteristics.