Get More Efficiency from the “Workhorse” Fuel

In a recent article on rising diesel prices, the New York Times referred to diesel as the “workhorse” of fuels. “Diesel powers a vast chunk of America’s economy,” the article states – everything from long-haul freight transportation to agriculture to construction and heavy machinery. Today, however, with overseas conflicts disrupting global oil supplies, all those industries are feeling the pressure of diesel prices approaching record highs (according to AAA, diesel prices have reached historically elevated levels in some markets). And that has a ripple effect across the entire economy, exacerbating inflation in everything we buy. As a result, the question of how to optimize fuel economy has taken on greater urgency than ever.

There’s some good news for diesel-powered trucking fleet operators. Between more aerodynamic vehicle design and increasingly efficient engines, the average miles-per-gallon for trucks on the road has steadily increased in recent years. Another important factor, not to be underestimated, is the trend toward lower-viscosity diesel engine oils.

Numerous industry studies have identified engine oil viscosity as one factor that can influence fuel economy. With a thicker oil, the engine simply has to work harder to make the oil flow to where it’s needed, which means burning more fuel. A thinner oil reduces the oil’s resistance, or friction, and therefore the engine doesn’t have to work as hard to push it through. This can help reduce fuel consumption and may improve engine efficiency, depending on operating conditions. While factors such as climate and duty cycle certainly come into play, in certain Chevron field and laboratory evaluations, fuel economy improvements of approximately 1% to 2% have been observed when switching from 15W-40 to 10W-30 oils.*  That may sound like a small increment, but amortized over a fleet of hundreds or even thousands of vehicles, it can have a real bottom-line impact.

The old line of thinking that a thicker oil means better protection has largely been disproven. Today’s lower-viscosity oils are subjected to the same rigorous testing and have to meet the same API performance standards as higher-viscosity fluids. In fact, many engine OEMs now specify or factory-fill certain engine models with 10W-30 oils, reflecting broader industry adoption of lower-viscosity lubricants.

We are also seeing a marked trend toward the use of API category FA-4 oils in a wider variety of vehicles. FA-4 oils were introduced in 2017 as part of the PC-11 initiative, and were specifically formulated to support the fuel economy attributes of then-new engine models. Because they were not backwards-compatible with older engines, uptake in the aftermarket was relatively slow. However, operators have increasingly incorporated FA-4 oils into their lubrication programs as newer vehicles have entered their fleets. CK-4 oils designed for backward compatibility still dominate the market, but even within that category, operators have many options for moving to a lower viscosity.

When PC-12 oils hit the market in January 2027, FA-4 and CK-4 will be replaced by FB-4 and CL-4 categories. FB-4 is expected to support continued development of thinner viscosity oils specifically formulated to support higher fuel economy standards in 2027 and subsequent model year engines. PC-12 also calls for reduced sulfur ash content in engine oils to support mandated refinements to aftertreatment systems. The accumulation of unburned ash in diesel particulate filters is a huge drag on fuel economy. Field and laboratory evaluations have indicated the potential for fuel economy benefits from ultra-low ash engine oils, such as Chevron Delo^® 600 ADF, in certain applications.

As always, we recommend talking to your Chevron representative about your specific requirements and your options for safely switching oils. Higher diesel prices are likely to be with us for a long time. Chevron and other lubricant producers are working closely with engine OEMs to find ways to optimize fuel economy and get more mileage per dollar spent at the pump. It’s useful to know that a simple oil change can help make America’s workhorse fuel work smarter.

*Actual results may vary depending on engine type, operating conditions and maintenance practices.