For the past several years, commercial truck engines have been engineered for optimum efficiency, resulting in tighter tolerances and higher operating temperatures. New, lower-viscosity engine oils are a perfect match to help optimize this efficiency. The challenge for fleets, particularly mixed fleets with older vehicles, is determining when these next-generation oils can be used.

American Petroleum Institute (API) CK-4 engine oils first became available in 2017. Compared to their predecessor (CJ-4), CK-4 oils provide improved shear stability, oxidation resistance, and aeration control. Also introduced in 2017, FA-4 oils provide the same benefits, in addition to significant improvements in fuel economy. While a low-viscosity, fuel-saving FA-4 oil may sound ideal, it is not recommended for all engines.

“FA-4 was rolled out in 2017,” says Barry Mandelbaum, lubricants engineer for Phillips 66 Lubricants. “Most OEMs are going to at least provide for the use of an FA-4 oil on their newer vehicles. If a fleet is looking to transition to an FA-4, a good starting point is to look at how many of its vehicles are 2017 and newer. The more FA-4 oil the fleet can consume, the more it makes sense to move in that direction.”

At the same time, a fleet comprising a comparable mix of newer and older vehicles could face some challenges. “If the fleet wanted to use FA-4 in its newer vehicles, but its older vehicles couldn’t accept it, the fleet would face the prospect of having to inventory two different oils,” Mandelbaum points out. “Most fleets prefer to inventory a single engine oil because it’s a lot easier to manage.”

Even if the transition to an FA-4 is a bit of a stretch for the time being, a fleet could still consider the use of a lower-viscosity CK-4. Fleets should consult their oil suppliers to help identify products that align with their specific needs and business objectives.

The trend toward lower viscosity

FA-4 is a lower-viscosity oil, generally a 10W-30. According to Dan Arcy, OEM technology manager at Shell Lubricants, new heavy duty trucks are now filled with 10W-30 at the factory, and 10W-30 is gaining popularity as the preferred viscosity for fleets. “We’ve essentially gone from a heavier, more viscous product to a thinner product,” Arcy says. “The great thing is that there has been no compromise in durability.”

James Booth, commercial sector manager at Chevron, agrees. “10W-30 has represented 100 percent of the U.S. HD OEM factory fill viscosity of choice since 2012, and we see it representing approximately 60 percent for large fleets. However, 15W-40 remains the dominant viscosity grade in the market,” Booth says.

Paul Cigala, CVL applications engineer for ExxonMobil Fuels and Lubricants, offers an explanation as to why.

“It’s kind of scary to say in the year 2020, but 15W-40 still dominates the market for heavy duty truck engines,” Cigala says. “That’s really around the mindset of, ‘My great-grandfather used 15W-40 and never had any problems, so don’t fix it if it isn’t broken.’”

The problem with that line of thinking is that innovation and continuous improvement cannot be embraced. There are some impactful benefits of switching to a low-viscosity oil when practical.

“Today’s new engines are really built around low viscosity, and low viscosity equates to [improved] fuel economy,” Cigala says. “That’s why we are starting to see a shift, especially among the larger fleets.”

According to Cigala, it has become clear that switching from a 15W-40 to a 10W-30 will result in a 1 to 1.5 percent improvement in fuel economy. Then, going from a CK-4 10W-30 to an FA-4 10W-30 will result in another 0.5 to 1 percent improvement.

The question for a mixed fleet is: When am I able to leverage these newer, lower-viscosity engine oil formulations?

CK-4 oils are designed to be backwards-compatible, meaning they can safely be used in older engines. FA-4 oils, on the other hand, have limited backwards compatibility. That is why FA-4 oils haven’t gained the kind of traction the oil suppliers and truck OEMs had anticipated.

“Detroit Diesel has been one of the early adopters of FA-4 oils,” Cigala points out. “They actually factory fill with FA-4. If you happen to be a fleet with a lot of DD Series engines, you’re in that sweet spot that can take advantage of an FA-4 oil right now.”

On the other hand, if you happen to be a mixed fleet with several older vehicles, the concept of backwards compatibility can be a major obstacle. Additionally, auxiliary power unit (APU) and reefer manufacturers have yet to offer approval or guidance around the use of FA-4 oils.

Tips on transitioning to newer oils

There is a new Technology & Maintenance Council (TMC) Recommended Practice (RP) in development to help fleets transition to new, lower-viscosity oils. Cigala is helping lead that effort. If all goes according to schedule, it should be published in fall 2021.

A primary objective of this new RP is to help fleets understand which types of engine oils can be used in which makes and models. It’s also important for mixed fleets to understand which oils can be used in certain types of engines.

“Legislation, incentives, and fuel prices have driven the industry to seek alternative fuels, resulting in an upturn in mixed fleet operations that include diesel, gasoline, and natural gas engines,” says Darryl Purificati, OEM technical liaison at Petro-Canada Lubricants. “The variation in fuel types makes maintenance more complex for technicians, and generally means that the workshop must stock a variety of lubricants to cater to each type of engine.”

Fortunately, some lubricant manufacturers have been developing products that address this challenge.

Petro-Canada’s Duron Geo LD is specially formulated for the high combustion temperatures in natural gas engines. Offered as either a 15W-40 or 10W-30, this oil is also ideal for heavy duty diesel and gas engines.

Shell’s Rotella T4 NG Plus 15W-40 is specially formulated for diesel, gasoline, and natural gas engines. Although it isn’t a low-viscosity oil, Arcy says this product still helps a fleet consolidate the number of oils it needs in its shop to service a wide range of engine types.

Fleets need to be particularly vigilant with any oil they are choosing for natural gas engines. As Chevron’s Booth points out, API has not set an engine oil specification for LPG/CNG oils to the extent it has for diesel and gas engines. “That is why Cummins’ specifications are largely followed, due to Cummins’ significant market share,” Booth says.

“Cummins is the dominant natural gas engine manufacturer for on-highway trucks,” Arcy adds. “Cummins specifies CES 20092 for its natural gas engines. It is imperative to use an oil that meets that specification in order to achieve proper protection and maximum oil drain interval.”

While some fleets service a wide mix of makes, models, and engine types, other fleets see less diversity in the bay. When that is the case, and the majority of trucks are no more than a few years old, Arcy is inclined to steer a fleet toward an FA-4 10W-30 for the fuel economy gains.

Petro-Canada’s Purificati says fleets should also consider lubricant type. “Offering better stability than non-synthetic oils, full synthetic and synthetic blend engine oils benefit from improved performance in varied weather conditions,” Purificati says. “Fully synthetic engine oils take advantage of specialized base oils to provide enhanced properties and longer life.”

The bottom line is that choosing the right oil depends on the complexion of the fleet, as well as the maintenance operation’s willingness to manage multiple engine oils in its shop.

“The most important thing is to understand the vehicles in the fleet, as well as their applications,” says Karin Haumann, product applications specialist for heavy duty engine oils at Shell Lubricants. “Then a fleet can work with its oil supplier to identify products that meet the least common denominator to reduce the number of oils that need to be inventoried.”

As appealing as simplicity is, the financial benefits of improved fuel economy may incentivize some fleets to begin transitioning to FA-4 sooner than later. Furthermore, the natural lifecycle of a commercial vehicle will cause the complexion of the typical mixed fleet to change over the next several years.

“As older engines transition out of fleets and are replaced by new engines, FA-4 oils will naturally become adopted,” Phillips 66’s Mandelbaum says. “But I think it’s going to happen slowly. As long as there is a high proportion of engines in operation that require the backwards compatibility of a CK-4 product, the logistical complications of having to manage two different oils will persist.

“The reality is that some OEMs have concerns about engine durability, which is why FA-4 has not been fully embraced yet,” Mandelbaum continues. “Phillips 66 has tried to split the difference by offering extended warranty support in some OEM engines that do not specify an FA-4 oil.”

Guardol FE 10W-30 with Liquid Titanium is an FA-4 oil. Phillips 66 has decided to extend its product quality guarantee to late-model vehicles: 2010 and newer Detroit Diesel engines, as well as 2014 and newer Cummins, PACCAR, Navistar, and Volvo/Mack engines.

Mandelbaum says Phillips 66 asks its fleet customers to provide a list of the makes and models its shop is servicing. “From there we can map out which vehicles can accept FA-4, and which can accept our Guardol FE with extended warranty,” Mandelbaum relates. “In some instances, we’ve been able to cover the majority of a fleet with FA-4.

“It also depends on the size of the fleet,” Mandelbaum continues. “If the fleet has numerous bays with tanks and hose reels and meters, investing in a second oil can be significant. There is also the challenge of making sure the correct oil is getting in a given engine. That is why shop organization is also key. You could have a very small shop where limited investment would be necessary to bring in a second oil. But if the shop isn’t very disciplined in how it handles its maintenance with documentation and labeling, that’s a major obstacle.”

Oil management best practices for the shop

The TMC RP under development aims to help fleets go through the thought process of how to effectively transition to FA-4 oil. If a fleet walks through the decision tree and concludes that it is time to begin transitioning to FA-4, the TMC RP provides guidance on implementation. “Here we talk about labeling, training, and working with oil suppliers to make sure everybody is on the same page,” ExxonMobil’s Cigala says.

Everything starts with training. Cigala says a typical “toolbox meeting” is an ideal venue. The fleet manager can make it clear to every technician that the transition is underway, along with the steps being taken to ensure a successful implementation. It may be possible to designate a single bay or two for vehicles capable of accepting an FA-4 engine oil. If FA-4 will be utilized throughout the shop, it’s important to label all tanks, dispensers, and hose reels.

Fleets should spend time thinking about oil storage. As Petro-Canada’s Purificati points out, adding a couple new engine oils to the shop could simply be a matter of adding them onto the existing lubricant shelving unit. “But doing that increases the risk of using the wrong product. The storage layout should be optimized, and a clear color-coded labeling system should be implemented,” Purificati recommends.

Cigala also recommends that color-coding can be a helpful approach. “A fleet may even want to add color-coded labels on truck dashboards or door jams, or maybe even tags on a dipstick or oil fill so it’s easy for a technician to know what a given truck and engine need,” he says.

Don’t forget about training drivers. As Cigala points out, drivers need to know which oil they are supposed to be using for top-offs. “A fleet may even want to put a container of oil in the truck to take the thinking out of it and avoid potential cross-contamination,” Cigala adds.

If a fleet decides that it would like to transition oils, the steps taken in preparation are very important.

“It is ideal for a fleet to draw down the tank and clean ahead of the product transition,” Chevron’s Booth says. “At the very least, a fleet should draw down to 10 percent or below heel before transitioning to a new product. Another best practice is to have the lubricant supplier conduct a compatibility check.”

Since FA-4 is still relatively new with limited applicability, availability is still a bit spotty. However, as fleets continue to age and cycle out older trucks, FA-4 supply and demand will naturally grow. “As more of the larger fleets begin to adopt FA-4 oils, we’ll start to see more availability,” Cigala says. “The other big key is when APU and reefer manufacturers decide to allow the use of FA-4 oils. Fleets want as few oils in the shop as possible.”

“The trend in the industry is toward higher-performance, more fuel-efficient engines – and that is not going away,” Phillips 66’s Mandelbaum reminds. “The appetite for FA-4 oils is only going to grow. To whatever extent a fleet can benefit from that, which from a fuel economy standpoint could be as much as 3 percent, I believe it is worthwhile to do so.”