Heavy-duty Engine Oil Specifications



The Diesel Engine Oil Advisory Panel met during the December ASTM Committee D02 meeting in New Orleans. As described in API 1509, the Engine Oil Licensing and Certification System, The DEOAP is a formally constituted committee composed of representatives from [American Petroleum Institute] and [Engine Manufacturers Association] member companies who deal with heavy-duty lubricant matters affecting the two trade associations.

The DEOAP will guide and facilitate the introduction of proposed heavy-duty performance categories. In addition to DEOAP members, liaison representatives from allied organizations-for example, [American Chemistry Council], SAE, ASTM, [Independent Lubricant Manufacturers Association] and the U.S. Army-may also participate.

Many topics were discussed, but one that caught my attention was about API FA-4 engine oils. API reported that there were over 1,350 CK-4 licenses in several viscosity grades. By contrast, FA-4, which is a lower-viscosity version of CK-4, had barely 100 licenses, which were overwhelmingly SAE 10W-30.

Why has this new, technically advanced oil not grown in the marketplace, even after being available for three years? After all, it was designed to reduce fuel consumption while providing advanced protection for the powerful heavy-duty engines.

If you go back to the start of the process to develop API CK-4 (then known as PC-11), there were certain factors that pushed the process forward. In 2011, the National Highway Traffic Safety Adminis­tration issued a regulation, which was to phase in from 2013 to 2018, that limited greenhouse gas emissions and for the first time required fuel economy improvements for medium- and heavy-duty trucks. This was a primary driver for PC-11. In June 2011, EMA asked API to develop a new lubricant category for the heavy-duty diesel engines being developed. PC-11-PC stands for proposed category-would offer performance beyond the time-tested API CJ-4 engine oils.

Through several iterations and after much discussion, the final CK-4 and FA-4 limits were established, tests were developed and precision studies were conducted to verify that the tests were measuring what they were supposed to measure. Finally, in December 2016, CK-4 and FA-4 were blessed and introduced. As is commonly the case, many oil marketers had their product changes and labeling ready to go, and the CK-4 introduction went off without a hitch. However, FA-4 lagged behind. The question is: Why?

Fifty years ago, when I was a fledgling oil guy, the heavy-duty engine market was split between two-cycle and four-cycle engine designs. The two-cycle market, owned by Detroit Diesel, had a strong appetite for low-ash SAE 40 oils, usually with a good slug of bright stock. They consumed about a quart of oil every 200 miles. With oil consumption like that, as long as the engine was in a reasonable duty cycle, there was no need to drain the oil, since the half-life of the engine oil was about 2,000 to 3,000 miles.

On the four-cycle side, there were Caterpillar and Cummins engine designs (among others) that had quite a different appetite for oil. They liked SAE 30 or SAE 40 oils with more ash and better stability. Drain intervals for these engines were in the 5,000- to 10,000-mile range.

Historically, fleets didnt like to stock more than one oil (and still dont), but there was no way they could avoid it if they had both two- and four-cycle engines in their fleets. However, in the mid 70s two-cycles began to fade from the scene.

It was then that some new interest in HDEO technology began to appear. The big move was to so-called universal oils. These oils were developed to cover both gasoline- and diesel-fueled engines. They became very popular, and soon multi-grade heavy-duty engine oil made its appearance.

Incidentally, for those who wonder why the heavy-duty API categories all have a 4 in the name, it is an artifact that means four-cycle. In the past, there were categories with a 2 included (for example, CF-2) that were for two-cycle engines.

SAE 15W-40 universal engine oil soon took over the heavy-duty market. There were a number of reasons why, but it boiled down to the fact that the base oil didnt need to contain bright stock, which many thought was detrimental to deposit formation. Use of SAE 15W-40 also resulted in less oil consumption than SAE 30 or SAE 40.

I was at Pennzoil at the time, and we had started working on a high-ash (1.5 percent) SAE 15W-40 oil, which we had documented would allow truck engines to go 1 million miles before overhaul with drain intervals of 25,000 to 35,000 miles. In addition, the SAE 15W-40 oil reduced oil consumption. The president of Pennzoil Products at the time disputed our claim of lower oil consumption and wanted proof. Our additive supplier came through with a description of the lower oil consumption claim based on thinner oil in the ring belt area, resulting in less oil being swept out. The boss was satisfied.

History made it difficult to move on from SAE 15W-40, since it gave lower oil consumption and good performance characteristics. That would become a major barrier to changes in viscosity but also demonstrated what fuel economy benefits could be extracted from engine oils. Incidentally, the OEMs had begun to use SAE 10W-30 for factory fill. With the introduction of API CK-4 and FA-4, we now have two SAE 10W-30s. The CK-4 variety has a high-temperature, high-shear viscosity of 3.5 centipoise or greater. FA-4 has an HTHS viscosity of 2.9 to 3.3 cP.

It seems strange that the very OEMs that requested API FA-4 were uncomfortable recommending it to their customers. Once you study the economics of the situation, it is a lot less confusing. The primary selling point for FA-4 is its fuel economy gains. In an earlier column, I reported that a 2 percent gain in fuel economy would be a major plus to fleet owners.

The flip side is the potential for earlier engine replacement due to excessive wear. The durability of the engine depends in great measure on the viscosity of the engine oil. If it is too low, premature wear can occur. Thats a potential warranty claim that the OEMs are concerned about.

For the fleet owner or owner-operator, if an engine needs to be replaced, the cost in addition to the actual hardware (around $15,000) includes loss of revenue due to downtime. Thats no small matter to a fleet operator, much less an independent owner-operator.

Of course, this all relates to over-the-road fleet operations. Operators for local and off-road operations share the same concerns and may not stand to gain as much from improved fuel economy.

For many, there is the issue of inertia. We all are guilty of dragging our feet when it comes to change. I had a note from one reader who stated that he always ran his oil changes on a 12,000-mile interval-even though his engine manufacturer recommended 30,000 miles-just because he had good success at the shorter drain interval. How much is comfort worth?

Fleet owners have other issues that cause them to delay changing to FA-4. Daimler North America is the only OEM to approve FA-4 as being backward compatible with pre-2017 engines. This means fleets with older trucks have to stock multiple oils if they want to use FA-4.

Another issue is that many fleets with auxiliary power units will need to carry another oil for these units, since they require a heavier viscosity. In some cases, its a simple matter of large fleets not having FA-4 in all of their service locations. Theres such a large cost benefit to switching to FA-4 that it might overcome their reluctance to stock a second oil.

I think it is obvious that there are several reasons for FA-4s slow start. But money talks, and right now it is probably yelling in OEMs and fleet owners ears! Lets move on to FA-4.

Industry consultant Steve Swedberg has over 40 years experience in lubricants, most notably with Pennzoil and Chevron Oronite. He is a longtime member of the American Chemical Society, ASTM International and SAE International, where he was chairman of Technical Committee 1 on automotive engine oils. He can be reached at steveswedberg@cox.net.