Last December, for the first time, the American Petroleum Institute started licensing two different approved heavy-duty diesel engine oils. CK-4 is the new backward-compatible standard, designed to replace CJ-4. A new FA-4 category was designed to offer a lower viscosity that performed under stressful conditions to help engine makers meet fuel efficiency standards.

CK-4 adoption is going largely as expected, but very few fleets are using FA-4 yet – because very few engine makers so far are recommending it.

Currently there are close to 600 licensed CK-4 oils and about 80 FA-4 oils, according to Kevin Ferrick, senior manager of API’s Engine Oil Licensing and Certification System.

CK-4 and FA-4 both have to meet the same performance standards in terms of things such as oxidation control, preventing engine wear, and protecting the aftertreatment system. They’re designed to be more robust and resistant to oxidation compared to their CJ-4 predecessors, says Brian Humphrey, OEM technical liaison for Petro-Canada Lubricants. “This may mean that, with proper oil filtration, longer oil drain intervals may be achieved. They are also designed to improve resistance to aeration and have increased shear stability, which will provide enhanced performance and greater hardware protection over time.”

But FA-4 is a different viscosity, and it’s limited to XW-30 grades such as 10W-30 and 5W-30. And that’s to offer better fuel economy.

Steve Phillips is president of Allied Oil & Tire in Omaha, Nebraska, a 59-year-old business with significant focus on the heavy-duty commercial truck market. Nearly all of its customers have transitioned to CK-4 – but none to FA-4.

“We spent about a year with the guidance of our vendors making sure we educated our customers on what that difference was,” Phillips says. “To me it speaks volumes as far as the fuel efficiency value that’s provided in moving to lower viscosities, which is something that some people are very uncomfortable with. But as people are seeing [their trucks] delivered factory-filled with 10W-30, they’re realizing these engines are tighter and more capable of handling the lower-viscosity oils.”

CK-4, FA-4, and viscosity

Adding to the confusion is that while you could have the same viscosity rating of 10W-30 in both CK-4 and FA-4 oil, the viscosities are not really the same. That’s because to meet the new FA-4 oil specs, oils must have a certain “high-temp/high-shear” viscosity rating that’s different from the basic SAE viscosity numbers.

“The important thing to know is a 10W-30 FA-4 oil is in essence a different viscosity than a 10W-30 CK-4 oil,” Ferrick explains. “The standards defining an FA-4 are in a different high temp/high shear viscosity range,” he says. “The viscosity measurement, the limit is different than the limit for a CK-4 oil. The net effect is the FA-4 10W-30 is a lower viscosity at the 30 range. The FA-4 10W-30 is in essence a lighter oil.

“The important thing to note is engines are designed with a certain viscosity in mind.” So if a CK-4 10W-30 is recommended, that’s the one you use, not the FA-4 10W-30, and vice versa.

FA-4: F is for fuel efficient

Although engine makers are the ones who asked API and oil makers to come up with an updated oil category for heavy-duty diesels, in part to address GHG/fuel economy standards, very few so far have approved the use of FA-4.

“I think they asked for it and now they have it and now they’re going to have to decide how they’re going to use it” to help reduce GHG emissions, Ferrick says.

“On the FA-4 side I think the market is not quite there yet,” says Stede Granger, Shell

OEM technical services manager. “Uptake is a little slow, understandably. It’s a brand new viscosity grade and some engine makers aren’t even accepting it.”

Detroit Diesel allows the most flexibility from a backward-compatibility standpoint, allowing the FA-4 oils to be used as far back as the 2010 model year.

At the other end of the scale, earlier this year, Ford told customers they need to avoid most new CK-4 or FA-4 oils and instead use a new Motorcraft diesel engine oil for the Power Stroke diesels used in its Super Duty trucks.

“Some aren’t ready to approve it at all, and others only for the new model year,” says Shawn Whitacre, senior staff engineer - engine oil technology with Chevron. “But I think that’s going to change over time; it isn’t necessarily unexpected.”

Even for motor carriers that have trucks in their fleet that can use the FA-4, it’s unlikely that they won’t have some older trucks for which it can’t be used. “Customers won’t be willing to move to these products until they are recommended for most or all of the engine types in their fleet,” Whitacre says.

Paul Cigala, commercial vehicle lubricant applications engineer for ExxonMobil, sees the same thing. “Fleets we talk with, I don’t care if it’s a mom and pop with 10 trucks or the largest fleet in the country with 14,000 trucks, they want one oil. They don't want the technician to put the wrong oil in the wrong trucks. And it’s not just your engines – you have to look at your APUs and your reefers.

“Most of our fleet customers are two or three years away from FA-4. Personally I don’t see FA-4 being relevant till we get to 2019 or 2020, when more OEMs will be allowing it.”

CK-4 Offers Improvements Over CJ-4 Oil

While there already are about 600 CK-4-licensed products, currently there are still 1,600 CJ-4 licensed products, Ferrick says, “so CK-4 has along way to go to catch up with that.”

For fleets that have been slow to change over, Ferrick notes that CK-4 is an improvement over CJ-4.

“CJ-4 has been around for about 10 years, so the standard itself relies on engine tests that were put in place to measure CJ-4,” he says. “CK-4 features two new engine tests that are more reflective of current technology. CK-4 is going to provide enhanced protection against oil oxidation, viscosity loss due to shear, advanced protection against oil aeration, catalyst [problems], particulate filter blocking, engine wear, and piston deposits.”

Confusion about protection

There’s still a fair amount of confusion out there about these new categories.

“Even though we are closing in on a full year after their formal introduction, I think there are still quite a few misconceptions in the industry regarding these new oils,” Whitacre says. “In some cases, fleets may believe that the new oils (both categories, not just the FA-4) are only recommended for newer engines. Some others believe that they are sacrificing protection by making the switch.”

Brian Humphrey, OEM technical liaison for Petro-Canada Lubricants, says the number one misconception fleets have about oils, especially the new categories, is that low-viscosity oils don’t protect as well.

“This is not the case, and the introduction of [API CK-4 and FA-4] was a big step forward in the evolution and acceptance of lower-viscosity engine oils. We know that there are a number of misconceptions surrounding low-viscosity oils across the industry, particularly the belief that they are not as protective as an SAE 15W-40, despite the fact that all major North American engine OEMs have been factory filling with 10W-30 oils for many years.”

Cigala says the biggest misconception he sees surrounds viscosity, as well. People think CK-4s are all 15W-40 and that you have to go to the FA-4 to get a lower viscosity. Not true. In fact, you can get 10W-30 viscosity in either CK-4 or FA-4 oils. So even though there’s not a big move yet to FA-4 oils, some fleets are looking at lower viscosity CK-4 oils, especially 10W-30s, to improve fuel economy.

Shell so far is seeing good acceptance on the CK-4 side, says Granger. Yet the majority of those fleets are still using it in the 15W-40 grade. He encourages them to consider moving to a lower viscosity with the new CK-4 oils. “We’ve done quite a bit of testing with all different brands of heavy duty diesel engine oil in Class 8 over the road trucks, and all seem to tolerate the 10w-30 CK-4,” he says. “For fleets still running 15w-40, definitely take a look at the 10w-30 CK 4. It’s what I would call a heavy 10w-30, but it would be a good step, and you get better cold temperature performance. Obviously once FA 4 is out there more and more engines out there that can accept it, [fleets still running 15w-40] would be farther behind where the industry is going.”

Longer drain intervals

Another benefit of the new oils is longer oil drain intervals.

“One thing we have seen is fleets starting to look at changing some maintenance practices, adopting new extended drains,” says Cigala. “Some fleets have looked at upgrading their products based on their duty cycles and optimizing oil drain intervals accordingly. Pretty much all of the OEMs raised their oil drain intervals by 5,000 to 10,000 miles on over-the-road trucks [getting] above 6.5 mpg, just based on the better performance of the new products.”

And, he says, fleets want to know how much of a buffer they have. “We know that nobody hits 30, 40 or 50,000-mile oil drain intervals exact. They want to know, what happens if it doesn't come back for another 5,000 miles, what’s my cushion there.”

One of the key factors in that answer is oxidation, and the new formulations “were really built around better oxidation stability.”

That’s because in today’s engines, “common rail, higher pressures inside the fuel injection systems, higher temperatures in the combustion chamber, the aftertreatment, have really put a lot of stress and strain on the oils,” Cigala says.

These new oils not only have better additives to prevent oxidation, but they also have better base stocks, he says. “The new formulations were not just tweaked CJ-4 formulations. They pretty much started from scratch, with new base stocks, new additives, better shear stability improvers. It’s a whole different mindset looking at this.”