Why PC-10 for ’07?

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Lubricant suppliers have just bellied up to a raised bar, and met requirements for the API CI-4 Plus oil classification. The new specs were designed to improve characteristics like soot dispersancy and anti-wear protection in new, hotter-running, low-emissions engines built starting late in 2002.

So, do we really need a new oil spec – temporarily referred to as Proposed Category (PC)-10 – for the next round of emissions reduction, slated to begin in 2007? Yes.

One reason is that most ’07 engines will use higher levels of exhaust-gas recirculation (EGR) to cool peak cylinder temperatures and further reduce oxides of nitrogen (NOx) emissions. This will cause the new engines to run even hotter, and require an oil with improved oxidation resistance. Fortunately, with ultra-low-sulfur fuel mandated for ’06, corrosion from fuel sulfur shouldn’t be as much of a problem as in the past; so new oil formulations won’t have to include as much ash to neutralize acid.

That’s good, because ’07 regulations have squeezed the allowable amount of particulate matter (PM) emissions so tightly that ’07 diesels will require diesel particulate filters (DPFs), which can easily be plugged or poisoned by ash and other traditional additives in engine oil.

“The maximum allowable ash will be 1 percent,” says Gary Parsons, manager, commercial automotive, North America, ChevronTexaco Global Products. In addition, “Phosphorous will be at 0.12 percent maximum, and sulfur will be at .4 percent maximum. It’s a chemical box that we all need to work within.”

“The chemical limits are there to preserve the aftertreatment (DPFs),” agrees Alex Bolkhovsky, commercial vehicle technical adviser, ExxonMobil Lubricants & Specialties. “We’ve had to reduce conventional, engine-protecting additives, but we’re working on new ones. Oil suppliers are working on this independently, but the industry is cooperating on testing development.”

There are batteries of tests, specific to each engine manufacturer’s lubrication concerns, and some of the tests are run with high-sulfur fuel to increase severity, and to ensure that the new oil not only will protect ’07 engines without damaging DPFs, but also will be backward-compatible – that is, that they’ll perform well in older engines and new ones that might be run on high-sulfur fuel.

“That’s a big concern,” says Bolkhovsky. “But overall compatibility has been the goal all along.”

“PC-10 will be backward-compatible,” adds Dan Arcy, technical marketing manager, Shell Oil, “but possibly at a modified drain interval.”

According to Parsons, pass/fail limits will be finalized in June 2005, and lubricants suppliers then will have approximately one year to qualify PC-10 products for introduction. Even after introduction, performance changes may continue, according to Arcy. “There were five spec changes after CI-4,” he says. “The same thing could happen with PC-10.”