Public Release: 

Cooking oils boost low sulfur diesel fuel and engine lubricant performance

Penn State

Penn State engineers have shown that adding specially treated cooking oils, such as soybean, canola or sunflower oil, to mandated low sulfur diesel fuels and engine lubricants reduces friction and wear.

Dr. Joseph Perez, adjunct professor of chemical engineering and leader of the project, said, "Low sulfur diesel fuels mandated in California will soon be required in all states to enable diesel engines to meet the 2004 emission regulations. Removal of sulfur from the fuel causes severe wear problems in fuel injector systems."

"We've shown that adding as little as 10 percent of a specially-treated mixture of vegetable oil and fuel reduces both friction and wear," he said.

"There has been concern that there might be an insufficient volume of vegetable oil to meet both food and fuel needs," Perez added. "However, our results show that when the vegetable oil-fuel mixture is oxygen-treated, you need only 2 percent vegetable oil to produce the same friction and wear performance as current high sulfur diesel fuel."

The Penn State team has also conducted tests with four vegetable-based engine oils mixed with proprietary additives and compared them with a commercial petroleum-based oil. Although differences were found among the oils, all of the vegetable-based lubricants showed equivalent performance in laboratory tests and improvement in lubricity over the petroleum product.

"The biodegradable oils are effective lubricants and have the potential to displace petroleum-based products in various applications including engine oils," Perez says. "Vegetable oils are renewable resources reducing our dependency on imported oil."

The Penn State engineer described the team's work most recently at the 39th Annual Technical Meeting of the Society of Engineering Science, being held at Penn State Oct. 14-16. Perez presented his paper, "Friction and Wear Studies of Fuel and Lubricants Containing Vegetable Oils", on Tuesday, Oct. 15. Perez's co-authors are Dr. Wallis Lloyd, adjunct professor of chemical engineering and graduate students, Kraipat Cheenkiachorn and Kimberly Wain.

The team also evaluated the role of particulate buildup on wear when new, extended use, non-vegetable diesel oils were used. The oils were run in diesel trucks and not changed for 75,000 to 100,000 miles. Make-up oil was added as required.

Perez noted, "Current diesel engine emission regulations require significant reductions of particulate material and nitrogen oxides. To meet these regulations, many engines use cooled exhaust gas recirculation systems, which force 5 to 15 percent of the exhaust back through an intercooler and into the intake air.

Although beneficial to the reduction of regulated emission, the system places severe stress on the lubricant since it must handle increased particulates, acidic components and water in the combustion zone from blowby past the piston rings."

The team's tests showed that wear increased with increasing mileage with the major contributor believed to be the particulate content of the crankcase oil. They note, "To solve these problems and meet the next round of emission regulations in 2007 is a serious challenge to additive and lubricant manufacturers and may involve a quantum leap in additive technology. Renewable oils may play a significant role in the development of these future engine oils."

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The extended use study was also reported at the Society of Engineering Science meeting at Penn State in a paper, A Study of Friction and Wear of Used Diesel Engine Oils." The research projects were supported by a chemical engineering tribology consortium including Cargill, Caterpillar, Cummins, NCAUR-USDA (Peoria, IL) and Valvoline.

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