At the recent Infineum Trends gathering in Los Angeles, it was noted that while SAE 15W-40 is still the dominant heavy-duty viscosity grade by volume in North America, theres been some growth in demand for lower viscosity grades such as SAE 10W-30. But the low cost of diesel fuel plus the lack of wide original equipment manufacturer support for FA-4 oils may slow the FA-4 adoption rate in the market. (As a reminder, FA-4 oils provide better fuel economy but have limited backwards compatibility.) SAE 10W-30 CK-4 oils, however, are becoming quite popular.

While large fleets are moving to SAE 10W-30, owner-operators will stay with SAE 15W-40, primarily because they are operating older vehicles and are very cautious with changing oil viscosity. Sales of Class 8 and off-road vehicles were down by about 20 percent in 2016 compared to 2015 due to overbuying and overcapacity, according to Infineum. 2017 also appears very iffy and could continue to be off, but current projections call for increases in 2018.

Its interesting that the move to lower viscosity oils isnt as apparent as expected, since CJ-4 and now SAE 10W-30 CK-4 oils have made some significant inroads in the last two to three years. CJ-4 is factory fill for all major OEMs, and seven of the top 10 fleets use it in their engines, including Ryder Fleet Management Solutions, which operates over 200,000 trucks in the United States using SAE 10W-30. Projections for 2027 show that sales of that viscosity will be essentially equivalent to SAE 15W-40, at around 42 percent each. Currently, SAE 15W-40 represents about 73 percent of the market, while SAE 10W-30 is about 15 percent, Infineum highlighted.

In addition to CK-4 oils, the major oil marketers also offer several grades of API CK-4/SN universal products. The new API guidance on universal oils states that for CK-4/SN products to be licensed, the oil must meet all tests and limits for both categories, depending on viscosity grade. In the past, CJ-4 and earlier categories were able to waive some of the test requirements in the S category for gasoline engines. This concerned the light-duty engine manufacturers, since they felt that some performance parameters were being compromised.

So, the OEMs requested the upgrade to CK-4. I will guess that you think they have all adopted CK-4, and youd be right. The case of FA-4 is a lot cloudier.

The problem lies in the high temperature high shear rate viscosity limits. CK-4 and earlier oil categories called for a minimum HTHS viscosity of 3.5 centipoise, high enough for CK-4 to work in older engines (backwards compatibility), a key goal for the industry. However, with FA-4, the HTHS limit is 2.9 to 3.2 cP. Will engines, especially older engines, be protected? The HTHS viscosity difference for FA-4 blows backwards compatibility out of the water for the new category.

One of the big changes that has come out of the successful introduction of CK-4 is that OEMs have extended their recommended oil drain intervals. However, some have also been promoting their own house brands because of performance concerns from the new diesel categories.

Cummins approves both CK-4 and FA-4 oils, but only those which meet its CES 20086 and CES 20087 specifications. The Cummins Oilguard program also allows extended oil change intervals with these oils, but only if used oil analysis is conducted using Cummins suppliers. If an operator uses Cummins-recommended Valvoline Premium Blue 8600 oil in its X15 engines, the manufacturer assures a 10,000-mile drain interval extension from 50,000 to 60,000 miles. Cummins and Valvoline claim the cost savings potential of using Valvolines SAE 15W-40 oil compared with conventional and synthetic blend CK-4 oils was upwards of $20,000 in annual oil maintenance cost and productivity savings for a 100-truck fleet.

Daimler North Americas subsidiary, Detroit Diesel, has issued a DFS93K222 specification for CK-4 oils and a DFS9K223 specification for FA-4 oils. Detroit Diesel is using FA-4 for factory fill in its DD13, DD15 and DD16 engines, boasting drain interval increases of up to 15,000 miles depending on engine model, and is also introducing a long haul specification for extended drain intervals.

Ford is recommending its new Motorcraft Super Duty engine oil for its Super Duty trucks. The company is warning commercial customers to avoid using most CK-4/FA-4 oils due to concerns about high-mileage wear rates. Instead, it is recommending CK-4 or CJ-4 oils with at least 1,000 parts per million phosphorus and requiring that fleets not use CK-4/SN oils unless they have been proven to meet the Ford WSS-M2C171-F1 specification. Fords 6.7L diesel engine is having high-temperature wear problems, primarily on push rods and rocker arm fulcrums and pads. Its Motorcraft Super Duty is needed to alleviate the problem.

International Trucks is promoting extended oil drain intervals with its A26 MAN Trucks-based engine family. The A26 features a variable geometry turbocharger that enhances reliability. Larger piston pins, connecting rods and bushings help optimize load distribution for enhanced durability, increasing service intervals up to 70,000 miles. Internationals recent alliance with Volkswagen may be a driving force for the extended drain intervals, which were pegged at about 40,000 miles prior to 2017.

Kenworth recently announced a 60,000-mile oil change interval for its fleet vehicles. It accomplished this by enlarging the oil sump and adding a centrifugal pump. The manufacturers Paccar division claims engine oil drain intervals up to 75,000 miles, increased from 60,000 miles. Kenworth recommends CK-4 oils and is planning to include FA-4 in the near future.

Mack has okayed the use of CK-4 oils in its engines and has also extended oil change intervals to a maximum of 55,000 miles, up from the CJ-4 level of 50,000 miles. Mack claims the new EOS-4.5 engine oil is a proprietary formulation that is better than CK-4 spec oils. This oil is backwards compatible with all engines using CJ-4 and CK-4 oils. Mack does not approve the use of FA-4 engine oils at this time. Volvo has been silent thus far, but is expected to use an approach similar to Mack.

Cummins and Valvoline started the proprietary engine oil trend in the U.S. a number of years ago with the introduction of Premium Blue. In Europe, two factors support OEM oils. First, there are few aftermarket maintenance shops, so truckers are required to use dealerships to do maintenance. Second, there arent many large fleets in Europe, and diesel OEMs can use the warranty lever (even though its not legal in the U.S.) to encourage the use of their proprietary oils.

I realize that this is not the end of the story. As engine developments continue to unfold, there will be more interest in lower viscosity. There is no specific fuel economy test at present for FA-4 oils. There is fleet data collected to show that SAE 10W-30 CK-4 offers fuel economy benefits of about 1 percent. The FA-4 version adds 0.5 to 1 percent on top of that.

One percent doesnt sound like much, but as we all know from the gasoline side, it is the cumulative effect that is so important. Taking Ryders 200,000-vehicle fleet and looking at the numbers based on 250,000 miles per year of operation, assuming 6 miles per gallon for fuel economy using SAE 15W-40 engine oil, I calculate that on a per-truck basis, a 1 percent improvement in fuel economy using SAE 10W-30 CK-4 to 6.06 mpg is worth a little over 400 gallons of fuel per year. Its not big savings, but when you multiply 400 gallons by 200,000 trucks it becomes 80 million gallons for the fleet! Wow! If you improve fuel economy by another 0.5 percent using SAE 10W-30 FA-4, thats an additional 40 million gallons. Double wow!

You can be sure that there will be additional work to lower viscosity further. Italian OEM Iveco is running an SAE 5W-20 Euro VI engine oil in Europe. Dont be surprised if the next step in the U.S. is something like Iveco level oil. And the beat goes on.

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 and SAE International, where he was chairman of Technical Committee 1 on automotive engine oils. He can be reached at steveswedberg@cox.net.