Art of fuel economy lubricant formulation: How appropriate fuel economy assessment tools and new technologies are opening-up new formulation spaces for the next generation fuel economy lubricants

Designing fuel economy lubricants is an art; finding the right balance between fuel economy and durability requirements is complex, with many trade-offs. To open new formulation spaces with ever increasing fuel economy, a deep understanding of how lubricating oils respond to different drive cycles, engine/transmission type and any coating properties, e.g. DLC, is required.

In this paper, we describe how the implementation of WLTC requires lubricant optimization to deliver improved fuel economy under this test cycle and therefore, lubricant viscosity reduction becomes more important. We also illustrate optimization of the sludge system is key to reducing overall viscosity of lubricants for ultra low viscosity application, such as in SAE 0W- 8 viscosity grade oils. To meet the cleanliness challenges in an SAE 0W-8 environment, we describe a developmental sludge handling system with improved cleanliness at constant viscosity to conventional SAE 0W-8 lubricants. A SAE 0W-8 demonstration oil with the developmental sludge handling system at equivalent sludge handling to a conventional system showed lower viscosity properties and demonstrated improved fuel economy performance in a motored rig test over baseline oil with a conventional technology.