More Complex Aftertreatment Systems Require Rethinking Oil Formulations

Fleets will need to extend DPFs as long as possible

More Complex Aftertreatment Systems Require Rethinking Oil Formulations More Complex Aftertreatment Systems Require Rethinking Oil Formulations
There was a time when diesel engine oil formulators’ primary concern was simply protecting the engine. However, as Euro 6 emission control regulations came into force, heavy duty OEMs began to develop sophisticated exhaust aftertreatment systems (EATS) in an effort to reduce nitrogen oxide (NOx) and particulate matter (PM) emissions. Oil formulators had to account for these new components, but initially that meant doing as little harm to them as possible. That is what led, for example, to the 1% ash limit in the ACEA E6 (E8) and E9 (E11) generations of engine oils, which are formulated to help control the buildup of unburned ash in the EATS.


Over the years, clean air standards have become increasingly stringent, and as a result, aftertreatment systems have become increasingly complex. A typical aftertreatment system today likely includes a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), diesel exhaust fluid injection (DEF) to decompose NOx, a selective catalytic reduction (SCR) system, and possibly an exhaust gas recirculation (EGR) system.


For lubricant formulators like Chevron, the implications are clear. We can no longer think of the aftertreatment system as something in the background that we can design around. Rather, we must look at the engine and the EATS as a whole and formulate lubricants that will protect both components.


DPFs take the brunt of punishment from today’s hotter-running engines. Ash and soot accumulation clogs the filters, which is a drag on engine performance and fuel efficiency – and a maintenance headache for fleet operators. Trucks have to be taken out of service in order to clean the DPF or moved to the side of the road to perform a forced regeneration, accelerating the engine to high temperatures to burn off soot. Some OEMs are now recommending that operators clean the DPF only once, then replace it when the ash accumulation returns to the point that it would require another cleaning.


The problem with that approach is that global demand for DPFs is skyrocketing. Europe’s latest emission standards will virtually require DPFs in all off-road diesel equipment. China and India, who together produce around 1.5 million heavy duty trucks a year, have introduced standards that will require DPFs in all on- and off-highway diesel-powered vehicles. Combine that with the fact that much of the precious metal needed to fabricate DPFs comes from Russia, and we have a very unstable supply chain issue that makes DPFs more difficult to acquire.


It is clearly in the fleet operator’s best interest to extend DPF life as long as possible while trying to minimize maintenance and regens. That brings us back to the role engine oil formulators need to play in protecting aftertreatment systems. The majority of the ash buildup in the DPF is attributable to non-combustible additives in the engine oil. Reducing the sulfated ash content in the engine oil can help prolong DPF service life and extend maintenance intervals. In 2019, Chevron launched Delo® 600 ADF specifically to meet that need, leveraging our patented ultra-low ash (ULA) technology to reduce ash by 60% compared to conventional E9/E6 oils, and dramatically slow down the buildup of ash in DPFs. Delo 600 ADF is proven to reduce DPF maintenance requirements and restore lost fuel economy.


Cleaner air benefits everyone, and we must all do our part to help meet emission goals, however aggressive they become. Lubricant producers have a particular responsibility to keep up with engine technology and help ensure that today’s complex aftertreatment systems do what they are intended to do: reduce harmful emissions. 


Discover more about Delo 600 ADF

About the Author Shawn’s career spans nearly 20 years focused exclusively on research and engineering dealing with heavy-duty engine lubricants, fuels, and materials. Before joining Texaco in 2013, he spent 12 years leading global fluids and materials engineering activities for Cummins. He also spent five years conducting lubricant, fuel, and emission research for the Department of Energy’s National Renewable Energy Laboratory in Golden, CO. At Texaco, he is a Senior Staff Engineer primarily responsible for product formulation of the Delo Brand of Heavy Duty Engine Oils. He is currently the lead formulator responsible for development of Texaco’s PC-11 product line upgrade. Whitacre is the new chairman of the ASTM Heavy-Duty Engine Oil Classification Panel, which is tasked with the final development of the Proposed Category 11 (PC-11) requirements that take effect in late 2016.

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