SANTA BARBARA, CA – A new generation of engine oils is in the North American market, passing a battery of tests developed for specific engine brands. But the work of convincing buyers about related features and benefits continues.

The transition from CJ-4 to CK-4 and fuel-efficient FA-4 categories has essentially been seamless, says Dan Arcy, Shell Lubricants’ global OEM technical manager, referring to formulas that were officially released in December. The chemistry was driven by ongoing calls for longer drain intervals, better fuel economy, lower emissions, and increasing horsepower, after all.

And these are hardly the engine oils that have flowed through pumps in years gone by.

Oxidation stability had to improve to handle higher under-hood temperatures. When oil oxidizes, it becomes acidic and thickens, Arcy explained during a media briefing in California this week. At the very least, that shortens potential oil drain intervals.

Tighter controls on aeration are especially welcome in off-highway applications, where trucks traveling up and down hills tend to suck air into the oil pump, breaking up the all-important layers of lubricant. Shear stability, meanwhile, had to improve to help keep oils from shearing out of grade into lower viscosities.

At this point manufacturers are all recommending CK4 engine oils, and many have also modified maximum drain intervals along the way, Arcy says. “There’s some caveats. There’s fuel economy requirements. There’s idle requirements.”

Cummins has increased standard drain intervals up to 50,000 miles with CK-4 or FA-4 formulas compared to the 40,000 miles with the CJ-4 that came before them, and will boost intervals up to 80,000 miles with its OilGuard Program. Detroit Diesel has pushed intervals up to 75,000 miles compared to the 50,000 miles with CJ-4. Navistar drains are up to 60,000 miles compared to the 40,000 miles with CJ-4, and pushes to 70,000 miles in approved cases. Paccar drains are up to 75,000 miles with CK-4 formulas, while Volvo and Mack drains are at 55,000 miles with CK-4.

Paccar, Volvo and Mack are the last holdouts in embracing the fuel-efficient formulas, although Arcy expects that could change in 2018. Cummins only allows FA-4 in the 2017 X15, while Detroit Diesels can use it back as far as EPA 2010 models. Navistar offers it as a factory fill on new A26 engines.

Off-highway applications are not using FA-4 yet either, although Arcy notes that these sectors have a history of lagging behind their on-highway counterparts when it comes to adopting new oils. The fuel-efficient oils are not yet recommended for diesel pickups, either.

Any rollout and approval takes time, but markets around the world are undeniably shifting to fuel-efficient oils. From North American to Europe, users are shifting from 10W30 to 5W30 as the grade of choice.

Engine manufacturers have also been able to introduce updated tests that need to be passed to ensure specific requirements are being met, and also update the components on which tests are based. Some of the equipment used to test earlier oil formulas, after all, was increasingly hard to come by.

Cummins introduced the CES 20086 and CES 20087 tests for its engines, Detroit Diesel has the DFS 93K222 and DFS 93K223 to measure protection against issues like liner scuffing, and there’s also the Volvo VDS-4.5/Mack EO-S-4.5.

One of the most noteworthy of the new testing requirements came from Ford, which only months before the rollout of the new oil category asked for phosphorous levels to be capped at 1,000 parts per million — measured in a specification known as WSS-M2C171-F1 — because of valvetrain wear noticed in its 6.7 liter engines. Those engines are also found in applications up to Class 7 and even the lower end of Class 8.

“Phosphorous is just one of the components that can be used as an anti-wear component,” Arcy says. In Europe, maximum limits have been set at 800 parts per million. But the Ford engine, which features 32 push rods, is relatively complex, Arcy says.

They aren’t the only way that the story of new oils continues to be told through ongoing tests. Shell itself has stressed that it is field testing the new oils in 350 vehicles.

“It’s real-world experience. You can’t beat that in terms of determining performance,” says Matthew Urbanak, heavy duty engine oil project leader. Since 2011 the company has amassed 60 million test miles on CK-4 formulations, and 50 million miles of tests involving High Temperature High Shear (HTHS) formulas. Fourteen engines running on CK-4 prototypes have been torn down, along with 19 engines running FA-4.

“We’re not seeing the wear concern. We’re able to formulate these products and meet comparable wear protection we see with CK-4,” says Urbanak.

Unwanted levels of soot, lead and oil consumption are all dropping. In the process, Total Base Number (TBN) and Total Acid Number (TAN) measures are becoming less relevant, Urbanak says. “We’re not seeing strong acids in the oil anymore.”

Then there are the potential fuel economy gains being realized with FA-4 engines. Shell, says Jason Brown, global technology manager for heavy-duty engine oils, is proving those benefits in real-world tests that reflect all driving conditions.

Measuring real fuel economy gains is no small task, however. “You’ve got to take real-world cycles,” Brown said. The World Harmonized Stationary Cycle is like on-highway driving. The World Harmonized Transient Cycle (Cold Start) reflects urban driving in cold-start conditions, sometimes cooling the engine below 0 Fahrenheit. And the World Harmonized Transient Cycle reflects urban driving in average temperature conditions to reflect stop-and-go driving like a UPS truck.

Shell is currently running a third-party fuel economy trial in Germany, will run one in Texas, and has completed another test series in China. “We’re talking about different OEMs, different engines, different operating conditions,” Brown says.

Shifting from a CK-4 10W-30 to an FA-4 10W-30 will boost fuel economy about 0.5%. A 5W30 FA-4 performs 3.19% better than a 10W40 in combined urban and highway driving cycles, Shell adds.

The push for oils to support improved fuel economy is not about to end anytime soon, either.

“This is going to remain a big, big topic going forward,” Brown says of the push to reduce greenhouse gases. “It’s about those engines running more efficiently, it’s about getting them to run more effectively.”

As much as there have been discussions about future power sources, Shell also continues to see a future in diesel.

Diesel will be the power of choice for most heavy-duty trucks, while electric motors will see their gains in urban cycles and light- or medium-duty applications, Brown says. He also added that Liquefied Natural Gas continues to be an option for heavy-duty trucks.

Yes, there will be changes in fuel and equipment as well as more electrification and hybrids, he observed. “Natural gas is going to be a very key fuel in the future. It’s very abundant. It’s very good on CO2 emissions.” Not only that, the engines are not significantly different from the diesel-powered options of today.

But one thing won’t change. “Diesel,” Brown said, “is going to be the main mover.”