Improved fuel economy should not come at expense of engine protection

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PARK CITY — Blending new low viscosity oils that improve fuel economy is a relatively easy process; ensuring they also deliver engine durability, however, is a tougher nut to crack. That’s the challenge motor oil manufacturers face as they prepare to formulate the new PC-11 category of motor oils intended to help engine manufacturers reduce carbon emissions.

Part of the problem, as Matt Urbanak, a chemist with Shell explained, is that viscosity of engine oils varies with temperature – the hotter the oil gets, the more its viscosity drops. Heavy duty engines redesigned over the past decade to reduce contaminants have been burning hotter. And there is concern that the engines of the future which will have to be designed to deal with the US Environmental Protection Agency’s new mandate to reduce greenhouse gas emissions by improving fuel performance could be running up to 10C hotter.

“Benefits of fuel economy should not come at the expense of engine protection,” Urbanak said.

Also interesting is that although the focus in coming years will be  on motor oils that help contribute to improved fuel performance, there is no formal heavy duty engine fuel economy test for motor oils.

“It’s simply understood that as you go to lower viscosity oil that fuel performance will improve. But every company has its own way to generate data and some companies may be a little less stringent than others in how they generate that data,” Urbanak said.

Urbanak said that Shell uses very high standards when it makes its fuel economy claims and that data is showing a measurable improvement in fuel performance when moving to lower viscosity oils such as 10W30s and 5W30s.  He outlined a series of tests that Shell has conducted over a 2.5 year period pitting low viscosity oils against the higher viscosity 15W40 oils the vast majority of the industry currently uses.

*The Shell Rotella T5 10W30 product showed a 1.6% improvement in mpg in comparison to the 15W40, using a Class 7, 2006 model year test vehicle with a 6-cylinder engine, under highway driving conditions over more than 2,500 miles. The test was conducted by an independent test facility in Ohio.

*The Rotella 10W30 showed a 3.3% mpg improvement versus the 15W40 blend in a Shell-run test using 9 Class 7 vehicles (model years 2000 to 2005) and running either Cummins ISC or ISM engines. The trucks were run 40% in the city and 60% on the highway for 13,455 miles. They were switched back and forth between the 10W30 and 15W40 blends every month for 12 months.

*The Rotella 10W30 showed 1.57% improvement in mpg versus the 15W40 blend in a test using a Class 8 vehicle running a Detroit Diesel Series 60 engine in on-highway conditions. The test was conducted by Schneider and complied with the SAE J1321 method.

Urbanak added that since the company’s launch of its Rotella T5 in 2009, analysis of its test truck engines, each of which have run over 800,000 miles, has shown excellent liner wear and cylinder liner bore polish protection in comparison to its 15W40 oils while piston ring protection has been on par.  Tests have also shown excellent piston deposit control at both the top (rocker arm cover) and bottom (oil pan) of the engine after 630,000 miles.

Wear results also look very promising in terms of iron, lead, copper and aluminum wear, Urbanak said. Same can be said for the viscosity control, soot handling ability and TBN retention and acid neutralization capability of the 10W30 oils in comparison with the higher viscosity 15W40 oils.

“We will continue to explore even lower viscosity formulations to deliver fuel economy benefits while delivering the same protection,” Urbanak said.

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