The lubricant of the day had to deal with the additional heat expelled by EGR cooling.
For 2007, engine oil had to be reformulated again so as to protect the diesel particulate filters, or traps, that were added to the exhaust stream that year.
As they approached the particulate filter, oil engineers knew they had to reduce the sulfated ash (material left after oil is burned), sulfur and phosphorus in their products — elements that inevitably would find their way into the exhaust and contribute to buildup of gunk in the filters.
Tiny particles of combustion-created soot attach themselves to the wall of the filter, and ash from burned engine oil accumulates on the face of the filter. Most of the soot is burned out of the filter in the regeneration process; but to clean out the ash, the unit is usually removed from the vehicle.
A new oil classification was built from the base up, the agents of ash were reduced and additives were selected to enhance wear protection and better control ring deposits, according to the oil vendors. Amajor goal was to reduce oil consumption as a factor in producing ash, thus extending the service life of the soot filters.
“None of the engine manufacturers told you then what their 2010 emission strategies would be,” said Shell’s Arcy. “They might have given you a glimpse of it, but a lot of them changed their positions later,” when they opted for SCR.
EGR and particulate filters remain the basis of all 2010 on-road truck diesel engines, regardless of size.
The biggest change facing truck operators is the addition of selective catalytic reduction, which renders harmless all but a trace of NOx byproducts of diesel combustion.
As an aftertreatment, SCR does not impinge on the engine lubricant.
Whether by design or luck, the CJ4 formulation was “a big enough bubble” or had “enough headroom,” as some of the oil people described it, to take diesel engines and emission systems into 2010 and beyond. Indeed, no new formulations are being planned at this time.
“I hate to disappoint [detractors], but we’re staying with mineral oil and CJ4 going into 2010,” said Ramin Younessi, Navistar group vice president of product development and strategy. “In fact, we’re going to push out oil change intervals a little, based on duty cycle and fuel economy.”
Those truck makers that have chosen to add SCR equipment and fluid to the exhaust have said that this choice lets the engine people dial back EGR and introduce more oxygen at the front end of the process.
SCR is an extremely efficient way of cleaning up NOx, industry engineers have said, so it is OK to produce more in the engine.
At Navistar, “rumor has it that we’re running so much hotter, the oil is going to break down,” Younessi said. “But we were able to extract heat from the base engine so that it’s running 10% cooler than it ran in ’07.”
That change was accomplished, he said, by redesigning all three elements of the coolant system: the radiator, the EGR cooler and the charge-air cooler for the turbo boost.
The company believes the in-cylinder solution is the best way to handle NOx production at its worst — during the transient cycle of multiple rpm revs as the driver shifts through gear and throttle changes.
Younessi was quick to raise the prospect of not only going forward with current CJ4 lubricants but actually extending oil drains as experience with 2010 equipment accumulated.
“For example, if you’re making 6.5 to 7.5 miles per gallon, we’re going to [recommend] extending drain intervals 10% to 20%,” he said. The goal is to get back to where most people were before all the need for emissions control was imposed by the federal government in the early aughts.
“Before EGR, everybody was shooting for oil change intervals of 50,000 to 100,000 miles,” Younessi said.
By Thomas M. Strah, Light & Medium Truck, April 2010