The lubrication industry as a whole has made tremendous progress in ash reduction over the past decade. Ultra-low ash technology is a game-changing breakthrough, achieved without compromising any of the protective benefits you expect from a CK-4 oil.
By Shawn Whitacre
Diesel particulate filters (DPFs) are un-questionably efficient and effective at doing what they are supposed to do, namely reducing harmful emissions from heavy duty diesel engines. However, the buildup of non-combustible ash in DPFs clogs the filters, impairing their performance and reducing their efficiency. Left unchecked for too long, DPF clogging can also impair engine performance and diminish fuel economy. That is why they require periodic cleaning, which is a maintenance headache for fleet operators. First, it is a costly and laborious process, usually involving a chemical treatment to break down the ash and special equipment to blow it out of the filter. What is worse, it requires taking a truck out of service for as much as a day, meaning downtime and lost revenue.
Ash Formation
The main causes of ash formation in DPFs are the metallic additives in heavy duty engine oils, whose formulations typically include calcium, magnesium, zinc, phosphorus, molybdenum and boron. To help minimize the accumulation of ash and the resulting maintenance requirements (and costs), a diesel oil based on a new, patented ultra-low ash (ULA) technology (Delo 600 ADF) was formulated with a novel additive package that has proven in exhaustive testing to be just as effective at wear protection, oxidation stability and oil life extension as conventional additives. More significantly, ULA technology reduces the ash content in the oil from the API-mandated maximum of 1 percent (considered “low ash”) to just 0.4 percent. This 60 percent reduction in ash content dramatically slows the buildup of ash in the DPF, meaning longer and more predictable maintenance intervals, while delivering a fuel economy benefit as well.
It has been suggested that operators can slow down DPF ashaccumulation with a conventional, 1 percent ash CK-4 oil simply by reducing oil consumption in the engine. One can see the logic in this argument—the less oil consumed, the less unburned ash flowing out through the exhaust aftertreatment system. And reducing oil consumption without compromising lubrication and protection is always a desirable goal.
Controlling Oil Consumption
As a practical matter, how do you actually control oil consumption? It is not as though there is a dial on the dashboard that you can turn up and down to regulate the flow of oil. This logic relies entirely on the ability of an oil to inhibit piston deposit formation in the power cylinder, which is the main driver of increased oilconsumption over the life of an engine. In other words, the rate of oil consumption depends largely on the properties of the oil being used and is otherwise out of the operator’s control.
On the other hand, the selection of an ultra-low ash oil is very much within the operator’s control and effectively guarantees minimal ash accumulation, making it a much easier and more predictable solution. Ultra-low ash oil exhibits remarkably good piston deposit control, so it will help limit oil consumption along with the specific and unique additional benefit of limiting ash buildup in the DPF. How much of a difference can a ULA oil make over the long haul? The most commonly used metric for oil consumption is miles traveled per quart of oil consumed. That figure is bound to vary widely from one engine to another, and oil consumption generally scales in proportion to fuel consumption. If an engine is working harder and burns more fuel, it will simultaneously consume more oil.
Let’s assume, however, an average oil consumption rate of 4,000 miles per quart. It might be much less in an older engine and far more in a brand-new engine, but that is a good starting point. After 400,000 miles, the engine will have consumed 100 quarts or 25 gallons of oil that pushes unburned ash through the exhaust system and into the DPF. Now consider whether all that oil has a 1 percent or a 0.4 percent sulfur ash content. Simple math tells us that an ultra-low ash oil is going to produce a fraction of the ash accumulation of a low-ash CK-4 oil.
Game-Changing Technology
Certainly, the lubrication industry as a whole has made tremendous progress in ash reduction over the past decade. The CK-4 standard represented a huge leap over previous generations. ULA technology is a game-changing breakthrough, achieved without compromising any of the protective benefits you expect from a CK-4 oil. Simply stated, if you really want to minimize DPF ash accumulation and avoid unpredictable maintenance and downtime, then you are better off with an oil specifically designed for that purpose. | WA
Shawn Whitacre’s career spans 25 years focused exclusively on research and engineering dealing with heavy-duty engine lubricants, fuels, emissions and materials. Before joining Chevron 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 Chevron, he is a Senior Staff Engineer primarily responsible for product formulation of the Delo Brand of Heavy Duty Engine Oils. Whitacre is the chairman of the ASTM Heavy-Duty Engine Oil Classification Panel, which was tasked with the final development of the API CK-4 and FA-4 specifications that took effect in late 2016. For more information, visit www.chevronlubricants.com/en_us/home/contact-us.html.