Chevron-Texaco aiming for backward compatibility

McGeehan explained that the creation of one oil to fully protect both older and new '07 engines poses major challenges but it is in the realm of possibility.

"From what we've looked at so far it looks promising, but the results of the field tests planned for this year will determine if it can be done," McGeehan said.

McGeehan said the new PC-10 oils need to be commercially available by the third quarter of 2006 so they can dovetail with the mandated introduction of low-sulfur diesel fuel, a fuel required for 2007 engine aftertreatment systems to work.

He also said PC-10 oil must severely limit ash residue, eliminate traditional wear inhibitors such as phosphorous and sulfur, and reduce engine oil volatility.

Complicating the situation is that low-sulfur fuel will be phased in between 2006 and 2010. The EPA has said that 80% of the fuel sold in the U.S. after June 2006 must be 15-ppm diesel, with the remaining 20% allowed to be 500-ppm diesel. After 2010, 100% of the diesel sold in the U.S. must be 15-ppm diesel.

Making PC-10 oil backward-compatible, however, may reduce oil drain intervals from where they are now, he noted.