Heavy-duty engine oils can have a major impact on two of the top three equipment-related cost areas for truck fleets: fuel and maintenance. Are you using the best oils for your fleet's bottom line?

According to an American Transportation Research Institute study completed last year, 8% to 10% of a fleet’s average marginal cost per mile over the past decade consists of maintenance and repair costs. And fuel costs ranged from 21% to 39% of that cost per mile.

Unexpected is more than an inconvenience for fleets. If a truck is not on the road, there are costs involved in getting it to a repair facility or fixing it on the side of the road. And while the vehicle is out of commission, it is not bringing in any revenue. On top of that, drivers are not making money while the truck’s not rolling. Businesses waiting for the delayed shipment are without the products or raw materials they were expecting.

How to minimize these disruptions and costs? Consistent preventive maintenance, including making sure you’ve got the right engine oil for your equipment and operations.

To that end, the API performance level certification helps fleet owners determine if their heavy-duty oils meet the needs of modern engine technology. Today’s CK-4 and FA-4 certifications provide improved oxidation control, shear stability and aeration performance. These factors can not only help prevent breakdowns but also improve efficiency and fuel economy.

Is the API donut enough to ensure that your engines will function at maximum efficiency and guarantee successful long-term performance? Not necessarily. The donut certifies the oil meets the category’s minimum requirements, but not all certified lubricants are created equal.

Recent research and testing have demonstrated that there are benefits to be had by selecting lower-viscosity grades, which can contribute to more efficient engine performance as well as fuel economy gains.

CK-4 vs. FA-4: A Quick Primer

API (the American Petroleum Institute) introduced the CK-4 and FA-4 service categories in 2016, and it marked the first time a new service category had been split in two. CK-4 represented a traditional category upgrade, providing some key performance upgrades versus the previous category (CJ-4) while remaining backwards compatible with all heavy-duty vehicles found on North American roads.

FA-4 lubricants, which are compatible with many 2017 model year and newer engines, were developed to deliver higher levels of fuel efficiency. With engine technology evolving, and newer engines running hotter and at higher pressures than previous generations of engines, FA-4 engine oils can deliver the needed performance at a lower high temperature high shear viscosity range (between 2.9 and 3.2 centipoise). This results in the engine running more efficiently, which translates into better fuel efficiency for the truck.

Lubricant Choice in North America

Traditional industry thinking has long held that thicker kinematic viscosity levels protect heavy-duty diesel engines more effectively than thinner ones, and that thinking is reflected in the market. Currently, 79% of heavy-duty diesel lubricants sold in North America are CK-4 15W-40, with the next closest viscosity grade of CK-4 10W-30 at 9%. FA-4 viscosity grades, meanwhile, have gained just a slim 1% share in the marketplace since their introduction.

However, as lubricant and additive technology has evolved, it has been clearly demonstrated that lower- viscosity grades can protect heavy-duty engines just as well as their higher-viscosity counterparts. Consider that all certified CK-4 and FA-4 lubricants deliver the same high levels of wear, oxidation, aeration, and other important performance characteristics. Consider also that many North American OEMs factory-fill their new trucks with CK-4 10W-30 lubricants, demonstrating their confidence that lower-viscosity grades can offer high levels of protection that fleet customers expect.

Lowering Your Fuel Costs

Why might you want to make the switch to a lower-viscosity grade? If a fleet has continued to use CK-4 15W-40 lubricants in newer trucks, switching viscosities is a choice worth investigating, if only to remain consistent with your OEM’s specification. Engines that have been designed to operate with a certain lubricant viscosity grade should be serviced with that same grade to maintain the protection benefits as intended by the manufacturer.

There are tangible bottom-line benefits to be had as well. Fuel costs represent a major opportunity for cost reduction for fleet owners, making up approximately 24% of a fleet’s average cost per mile, according to ATRI. If a fleet is using a CK-4 15W-40 formulation, evidence shows that achieving a cost reduction here can be done simply by going to a lower viscosity.

A joint report from the North American Council for Freight Efficiency and Carbon War Room shows the benefits: “Class 8 over-the-road fleets can realistically expect fuel savings in the range of 0.5% to 1.5% by switching from 15W-40 to 5W/10W-30 engine oil,” the report says.

If many of your trucks are model year 2017 or newer, it’s worth further consideration of making the switch to FA-4 lubricants, where even more fuel economy benefits can be had. The NACFE report highlights this point: “The savings from switching to the fuel-efficient FA-4 variant (FA-4 XW-30 vs CK-4 XW-30) … can be expected to add a further 0.4% to 0.7% of increased fuel efficiency.”

Interested in Moving to Lower Viscosities?

Switching to lower viscosity throughout your fleet is a significant operational decision, and it is not one that should be done lightly. Armed with an understanding of how and why low viscosities may be beneficial to your bottom line, a good first step is to start a conversation with your engine oil supplier and how it can support a switch. Your supplier may be able to help you run some testing with lower-viscosity lubricants to make sure they fit into your specific operational needs before adopting them fleetwide.

It is also important to consider the recommendation of your OEM. As noted, many OEMS factory-fill with 10W-30 grades, and fleet owners should prioritize remaining consistent with the manufacturer’s recommendation. And as more and more new-model vehicles enter your fleet, be sure to know whether FA-4 lubricants are recommended. For instance, Detroit Diesel began factory-filling with FA-4 formulations in 2017 and now has approved FA-4 for use in model years dating back to 2010.

It has, in fact, been increasingly shown that FA-4 lubricants are suitable for use in a variety of engine types. Lubrizol has field-tested FA-4 lubricants in real-world engines from a variety of OEMs, generating more than 86 million miles of testing. Trucks our teams have tested include new models designed to be filled with FA-4 lubricants as well as older-model trucks where FA-4 is not specified by the manufacturer. Through this testing, what we’ve found is clear: Engines, old and new, are demonstrating expected levels of wear at up to 500,000 miles of service while demonstrating significant fuel economy improvement.

For all these reasons, forward-thinking fleet owners should not rest on their laurels when it comes to selecting an appropriate engine oil formulation to service their trucks. Lower-viscosity formulations — of both the CK-4 and FA-4 varieties — can lead to significant fuel economy savings and bottom-line benefits.  

Author Greg Matheson is product manager, heavy-duty engine oils, for The Lubrizol Corporation, which provides specialty chemicals for the transportation and other markets, including additives for engine oils. He has been with Lubrizol for more than six years and previously worked for TravelCenters of America. This article was authored and edited according to HDT editorial standards and style to provide useful information to our readers. Opinions expressed may not reflect those of HDT.