On the specification front, to support fuel economy drivers and the introduction of new emissions reduction hardware, the American Petroleum Institute, or API, introduced the CK-4 and FA-4 categories on December 1, 2016. In addition to being eco-friendly, the new standards deliver improved engine aeration performance, reduced wear, more robust protection against deposit formation, increased oxidation control and better shear stability over API CJ-4. What’s more, API FA-4 introduced SAE XW-30 grades with a high temperature, high shear (HTHS) viscosity range of 2.9 centiPoise to 3.2 centiPoise for on-highway applications.

To meet those specifications, a rapid shift toward SAE 10W-30 oils is expected. By 2029, SAE 10W-30 may account for roughly 40% of the market. SAE 5W-30, although not reaching mainline volumes, could make up about 10% of the market. The growth of even lower SAE XW-20 viscosity grades, however, is likely to be a slow process that depends on further innovations by heavy-duty original equipment manufacturers.

North American HDD Viscosity Trends

On a positive note, heavy-duty diesel fleet owners and operators are becoming increasingly comfortable with API CK-4 SAE 10W-30 fluids. It is important to note, though, that some are still hesitant to use lower-viscosity API FA-4 oils if they are not explicitly supported across the entire fleet. 

It is essential to note that in the quest for fuel economy, the introduction of lower-viscosity grades does not compromise the durability of the engine or the compatibility of emissions systems. Additives are designed to help ensure lubricants can function at much lower viscosities and retain their protective properties over the course of ever-extending drain intervals.  

New lubricants provide enhanced fuel economy via their viscometric and frictional properties and enable the introduction of new engine technologies that provide significant increases in fuel economy and engine performance under more extreme operating temperatures.  

Furthermore, the fuel saving benefits of lower-viscosity lubricants are too great to be ignored. With the continued support of OEM specifications, lower viscosity grades will continue to grow in use.  

Advantages of Switching to Low-Viscosity Oils

Viscosity is an engine oil’s most important property. Engine oil viscosity should go low enough to flow at low temperatures and high enough to protect and perform at high temperatures. 

Beyond regulatory issues, what factors are driving the lower-viscosity heavy-duty engine oils trend? 

First and foremost, heavy-duty engine oils can offer unprecedented fuel economy benefits: 

• Decrease Greenhouse Gas Emissions. The principal way to lower carbon dioxide levels is to improve fuel economy (i.e., burn less gas or diesel and decrease pollution).   
• Fuel Savings. A commercial truck can easily consume more than $70,000 (20,500 gallons) of diesel fuel per year. A switch from a 15W-40 oil to a properly formulated 10W-30 oil can result in up to 3% fuel savings through outstanding oxidation performance.

How Low Is Too Low?  

More OEMs are adopting 10W-30 CK-4 heavy-duty engine oils for their factory-fill, and some are going even further with FA-4 selections. OEMs provide valuable resources regarding allowable limits on viscosity grades and oil drain interval extension. When it comes to viscosity, thicker is not always better. Rather, a balanced formulation proven to provide engine protection as well as fuel economy benefits should be considered.

Automotive Lubricant Viscosity Grade, Engine Oils (SAE J 300SEP2015)

The good news is that newer truck engines are fitted with certain enhancements—such as polymeric coatings—that allow for improved fuel economy and friction protection. As a result, modern engines—which are often smaller, hotter running, higher output engines—are designed to operate on the SAE 10W-30 oils that are more common today.

Are Low-Viscosity Oils the Answer to Fleet Engine Needs? 

Switching to low-viscosity heavy-duty products will help to give fleets’ engines the efficiency to deliver more. The many benefits of low-viscosity products are listed below: 

• Properly formulated low-viscosity oils offer improved engine durability, extended engine life, enhanced performance and increased protection in both old and new engines. 
• Several types of engine oils can be formulated to have a low viscosity, including oils used to lubricate heavy-, medium-, and light-duty off-road vehicles as well as commercial on-road vehicles and stationary diesel engines.  
• Most low-viscosity products are approved or suitable for use in engines designed by leading heavy-duty engine manufacturers, including Ford, PACCAR, Volvo, Caterpillar, Cummins, Mack, Detroit Diesel and Mercedes-Benz. 
• There are multiple options, such as API CK-4 and FA-4 engine oils, that will fit unique fleet and heavy-duty diesel operations.
• Some heavy-duty engine oils, such as CITGARD, are guaranteed to reduce the total operating cost, improve fuel efficiency and improve carbon footprint. Fuel economy remains a concern for fleets as fuel costs continue to top the list of vehicle-based motor carrier costs. Low-viscosity oils like CITGARD 700 can reduce fuel consumption in fleets switching from a 15W-40 CK-4 oil to a 10W-30 CK-4 oil by up to 3%. (See the Brundage-Bone Case Study below.) 

OEM Engine Oil Recommendations

Fuel Economy Increases: A Case Study

Brundage-Bone Concrete Pumping Company was established in 1983, with headquarters located in Denver, Colorado. Brundage-Bone has an impressive national presence, with 80 branch locations in 22 states. Its fleet is comprised of 482 trucks, including line pumps, telebelts, Tremie tips and other specialty pumping equipment from such brands as Putzmeister, Schwing and Alliance.  

The largest concrete pumping company in the United States, Brundage-Bone operates the most extensive and diverse fleet of concrete pumping vehicles and equipment in the nation. Reducing annual fuel costs—the company’s largest expense—improving equipment availability and operational efficiencies are the company’s top business priorities. 

U.S. On-Road Fuel Economy

After more than 10 years with their former lubricant supplier, Brundage-Bone partnered with CITGO to supply lubricants in line with Brundage-Bone’s evolving requirements. With the market shifting to lower-viscosity oils and the potential cost savings associated with them, CITGO presented tools and resources to help Brundage-Bone analyze its equipment and fleet to gain insights on how low-viscosity engine oils, specifically formulated for improved fuel economy, could help meet its goal of lower fuel costs. 

Following consultations with CITGO technical experts, Brundage-Bone successfully transitioned its 450-unit fleet operation to CITGARD 700 heavy-duty engine oil. 

Six months of careful evaluation of fleet performance data from Brundage-Bone’s third-party independent telematics solutions provider showed that Brundage-Bone realized up to 2.5% annual fuel cost savings by switching to CITGARD 700 Synthetic Blend SAE 10W-30.

Today, the CITGO team works closely with Brundage-Bone’s general manager and its national service manager to continue to understand the company’s overall lubrication program as well as its goals for reducing the company’s fuel costs and gas spend per mile before making recommendations that would benefit its operations.  

“Our relationship with CITGO has grown from a commodity supplier to a partnership, which is a stark contrast from what we experienced before,” said Mark Young, general manager with Brundage-Bone. “The team has been very helpful, navigating us through the challenges that can come with switching vendors and product lines. It’s gone smoothly. Our company representatives are confident knowing there is a team of people dedicated to supporting them—and us—very well.”

Brundage-Bone named CITGO as its preferred lubricant supplier, and the concrete pumping giant has adopted other CITGO lubricants—including hydraulic fluids, greases, gear oils and concrete release agents—for its operations. 

The Bottom Line

Steven Bowles is a senior product specialist with CITGO. He holds both STLE CLS and OMA I certifications and has more than 16 years of experience working in laboratory and analytical chemistry.