Clean Oil Reduces Engine Fuel Consumption

Jim Fitch in his column in the Machinery Lubrication magazine discussed the important role of lubrication on energy conservation and environmental protection. A case in point was, "the impact of clean oil on fuel consumption and emissions in engines".

When a lubricant degrades, it forms reaction products that become insoluble and corrosive. So too, the original properties of lubricity and dispersancy can become impaired as the lubricant ages and additives deplete. However, surprisingly little has been said about the impact of fine abrasives in lube oil as it relates to fuel economy over the life of the engine. Fitch listed several scenarios:

• Anti-wear additive depletion
• Combustion efficiency losses
• Frictional losses
• Viscosity churning losses
• Stiction losses

A bus engine fuel consumption study by G. Andrews, et al. of the University of Leeds noted that the Cummins engine's fuel efficiency increased 2 percent to 3 percent when a six-micron by-pass filter was used along with a full flow filter. Also using by-pass filtration, a 5 percent to 8 percent reduction in fuel consumption was achieved.

J. Fodor and F. Ling study reported in Lubrication Engineering found a sharp improvement in fuel economy in a diesel engine when fitted with improved filtration. By reducing oil contamination by 98 percent, not only was there a 5 percent reduction in fuel consumption but wear and friction were reduced by 93 percent and 2.9 percent respectively.

When the engine consumes oil, due primarily to contaminant-induced wear, oil enters the combustion chamber, burns with the fuel, and is pushed out with exhaust gases as particles and volatile hydrocarbons. Unlike a new engine, the lubricating oil is a dominant contributor to particulate matter (PM) emissions in aged engine.

Reference
Staley, D.R. (1988). "Correlating Lube Oil Filtration Efficiencies with Engine Wear". SAE. Truck and Bus Meeting and Exposition (Paper 881825).
July-August issue of Machinery Lubrication magazine