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Soot 'N Stuff

by Jim Park

We’re headed for another change in engine oil formulation in 2007. With the exception of Caterpillar’s ACERT engines, all ‘07 diesels will run at a higher EGR rate than current engines do. “Somewhere between 13% and 30% at cruise speed,” says Petro-Canada’s category manager for commercial transportation lubricants, Jim Putz. “But at idle we could see EGR rates as high as 70%.”

That means soot is going to be more of an issue in 2007 than today. Not the stuff going up the stack, but the soot that winds up in the crankcase. Soot will foul the expensive diesel particulate filters (DPF) mandated for ‘07, so in a way, soot winding up in the crankcase isn’t bad – from that perspective. The ability of the oil to keep those fine particles suspended, preventing them from clumping up in some remote oil gallery and clogging a vital oil path, will be the job of the new PC-10 oils.

On top of that, there are concerns about oil making its way up into the combustion chamber. Oil contains sulphated ash, which helps neutralize acids formed in the combustion process. We don’t want ash clogging up the DPF, either. So, the PC-10 oils will need to have lower sulphated ash content (in the range of 1%, down from 1.5%) than today’s oils, and, on top of all that, the new oils need to be backward compatible with existing and older engines. That’s a heck of a tall order.

On the upside, when Ultra Low Sulphur Diesel (ULSD) finally hits the market, the lower sulphur content will help reduce the formation of sulphuric acid in the crankcase. “The potential benefit here is longer drain intervals,” says Dan Arcy, technical marketing manager for Shell Lubricants. “Less acidic oil will keep the additive package intact longer, possibly allowing for longer drains. We believe this will be a benefit on pre-EGR engines. We don’t know yet, absolutely, how soot loading will affect drain intervals on the ‘07s.

“Now, acceptable soot loads are in the 2% to 3% range. The engine makers now are asking for higher soot handling capacity,” Arcy says.

Petro-Canada has identified synthetic oils as a means of maintaining or improving drain intervals. According to Putz, synthetics have better soot suspension capabilities, and, you can get away with a lower viscosity oil.

“We’d be marketing 5W-40 or 10W-40 as a heavy-duty oil rather than the current 15W-40,” he says. “You’d get better cold weather performance in the winter and no thermal degradation in the summer.”

Bear in mind, there are a limited number of ‘07 engines in field tests now; the oil engineering is by no means complete. While both Arcy and Putz stress that their products will meet the ‘07 challenge, they’re still fine-tuning their formulations.

“We’re ahead of the game on the testing at this point,” says Arcy. “We know what the engine makers want, and were testing in the field and in prototypes.”
Putz says premium Group II base stocks will become more prevalent. “Heavy-duty engines will need the purest base stocks possible,” he says. “And we’ll be blending with ashless additives to keep the ash content within spec.”

One thing that’s almost a certainty, the new oils will be the best engine lubricants we’ve ever seen. We may not gain much in terms of drain intervals with the ‘07 engines, but neither Arcy nor Puts expect to lose ground on that front. For owners of older engines, the gains in drain intervals might be significant. H

Will We Need Extra Filtration in ‘07?

According to Dave Taber, technical coordinator for heavy-duty engine oils at ConocoPhillips, Mack had some problems with viscosity increase in fleet engines when the CI-4 oils were introduced for the ‘02 engines – the oil got too thick because of the amount of soot in it. Mack offered larger filter capacity and a fast spinning CentriMax centrifugal separator to remove the soot. Adding centrifugal filters or additional bypass filtration might be a way to maintain or even improve drain intervals for everyone come ‘07.

Supplemental filtration helps remove finer particles from the oil, too.

By-pass filters typically use a finer media, which slows the flow of oil through the filter. Full-flow filters must maintain a certain flow rate, and that imposes limits on the "fineness" of the filter.

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