THE SHIFT TOWARD LOWER VISCOSITY OILS
North America is behind Europe in the use of lighter oil viscosity grades (around 80% of the U.S. market uses 15W-40 oil) for heavy-duty diesel applications, but this is changing. Because of the aggressive drive toward ever-increasing fuel economy, lighter viscosity grades that contribute to it are slowly becoming accepted.
For example, there is currently an increase in 5W-40 oil usage. Shell reports that its Rotella T Synthetic 5W-40 can help improve fuel efficiency by up to 1% when compared to conventional 15W-40 motor oil. This is achieved through decreased friction and reducing the energy used to pump the motor oil through the engine. For a typical truck traveling 100,000 miles per year, a savings of up to 140 gallons per year, or $532, may be realized (based on $3.80/gallon of fuel and fuel consumption of 7 MPG).*
Joan Evans, Infineum industry liaison advisor, reports that similarly for passenger car motor oils, the new ILSAC GF-6B specification was proposed to accommodate the immediate needs of some OEMs for lower viscosity oils. Since the older engines were not designed to run on these lower viscosity oils, there is the potential for significant engine wear, (particularly bearing wear) if misapplication of these lower viscosity oils in older engines occurs.
Chris Castanian, OEM liaison manager for Lubrizol in Wickliffe, Ohio, says, “An absolute given is that engine oils have to provide engine durability. Saving fuel is a benefit built on top of engine protection. In both GF-6 and PC-11, discussions are underway on how to identify these new ultra-low viscosity oils to avoid misapplication. Going forward low viscosity oils and engine oil additive technology hold great promise for lowering greenhouse gases and improving fuel efficiency, but issues of backward compatibility and misapplication need to be addressed.”