Advancement in Heavy Duty Diesel Engine Oils has, for approximately two decades, been driven by the ever more stringent emission legislation for NOx and Particulates. Over the last few years, the focus has shifted to reducing CO2 emissions, which created an interest in fuel efficient lubricants. In addition, increased fuel cost and a need to control operational expenses in a weaker economy have further heightened the interest in fuel efficient lubricants. Where the trucking industry was reluctant to move away from the tried and true SAE 15W-40 viscosity grade, there is now a strong interest in pushing the boundaries of lower viscosity to reduce internal friction in the engine and thereby improve fuel efficiency. Consequently, the industry is exploring and introducing lower viscosity grades, such as SAE 10W-30 and even SAE 5W-30.
Fuel economy research work, looking at viscosity reductions as a means to improved fuel economy, was expanded to also evaluate the fuel economy improvement potential for changes in the additive chemistry. None of the previous diesel engine oil specifications included fuel economy as a design parameter. However, it was found that it is possible to take fuel economy to a next level, a level beyond that what can be reached with a simple viscosity reduction, if the chemistry of the additive package is optimized for friction control. This publication describes the tools and the research that paved the way to take the fuel economy performance of a new generation of diesel engine oils to the next level.