HAMBURG, Germany — As work continues towards the development of a new heavy-duty engine oil category, presently known as PC-11, early indications are that fuel savings could be in store for fleets.

The API PC-11 engine oil category is slated to be rolled out to industry in 2016. While engine oil categories can be a difficult thing to get excited about, early test results from Shell suggest fleet owners may have much to look forward to in this particular changeover. Typically, emissions mandates have driven new engine oil categories roughly every four years. By the time PC-11 hits the market in 2016, the current CJ-4 category will have been on the market for a decade, which Shell’s global OEM technical manager Dan Arcy said is a testament to the effectiveness of the CJ-4 specification.

All good things must come to an end, however, and CJ-4 will eventually be phased out by the new category, which was designed to handle the increased engine temperatures – to the tune of +10 C – expected of the next-generation engines, as well as other challenges.

Arcy has been actively involved in developing the PC-11 test requirements. Among the areas to be tested and improved upon are: oxidation stability; aeration benefits; scuffing/adhesive wear; shear stability; and compatibility with biofuels.

Noticeably absent among those requirements is a fuel economy test. The industry is now wholly convinced that lower viscosity engine oils do, in fact, provide better fuel economy, and so it was agreed that no further testing of this theory was required.

Low-viscosity engine oils – generally those of a grade of 10W-30 and lighter – have figured prominently in discussions around the new standard; not surprising, since it’s expected low-vis oils will be required, or strongly recommended, to comply with impending greenhouse gas emissions rules in the US and Canada. In fact, PC-11 will have two sub-categories: one validating the performance of conventional 15W-40 and heavier oils, and another category for lighter-weight products.

While it’s now widely accepted that low-viscosity oils provide fuel savings of about 1.6% (for a 10W-30 oil, compared to a 15W-40), concerns remain about the lighter-weight oil’s ability to provide protection equal to that of a conventional 15W-40.

Those concerns seem to have been mostly put to rest, based on extensive testing conducted by Shell.

“The concern in the industry is there will be more valve train wear, more wear in the piston ring liner area and more bearing wear,” Shell’s Keith Selby said at a global press event on heavy-duty engine lubricants, held today at the company’s sprawling Technical Center in Hamburg, Germany. “The industry is currently working to enable the use of low-viscosity oils and maintain current levels of engine durability. The good news is, the data shows future engine oils can match current wear protection with conventional engine oil grades.”

Arcy pointed out tests conducted by Shell showed that after 829,000 miles using Shell Rotella T5 10W-30, rocker arms, oil pans and cylinder liners were as clean and in as good of condition as those in similar trucks running 15W-40 oil. The lighter-weight oil also demonstrated excellent iron wear protection, strong TBN retention and acid neutralization capabilities, Arcy said.

“10W-30 oils can provide the wear protection you need, even in extended drain conditions,” he said.

As the PC-11 category is further developed, one term you’ll want to add to your trucking vocabulary is: High Temperature High Shear (HTHS). This has become an industry-accepted method of measuring viscosity and is expressed in centipoise (cP). Industry wanted a more precise way to define viscosity, since not all 40-weights are created equal. Rotella global brand manager Chris Guerrero compared those engine oils to a high school football team, where all the players may be in the same grade, but some players are much bulkier than others. Likewise, some thick 40-weights are over-engineered while others more closely resemble a 30-weight. Adopting HTHS allows the industry to better understand the true specifications of a low-viscosity engine oil.

To give an example, a current 15W-40 oil typically weighs in at about 4.2 cP. “That’s towards the upper end of a 40-grade, where most 15W-40s are blended,” Arcy explained. Thirty-weight CJ-4 oils are typically around 3.5 cP.

“The current proposal is for a range of 2.9 cP to 3.3 cP and it may even go lower than that,” Arcy said. This is good news for fleets looking to save fuel. Arcy said Shell has found that moving from a 4.2 cP oil to a 3.5 cP product has demonstrated in on-highway field trials, fuel savings of 1.6%. Moving from 3.5 cP to 2.9 cP will bring further fuel savings. Fleet managers and owner/operators, however, will have to be savvy buyers, as this number won’t likely be prominently displayed on packaging. It will behoove the buyer to seek out the HTHS rating, which will be included on data sheets.

The fly in the ointment of this improved fuel economy could be backwards compatibility, which Arcy said may not be possible with oils that boast the lower cP measurements.

“They may not be able to be used in older equipment, and that could be a challenge for some of our customers,” he acknowledged. “They have equipment that spans multiple years, so there are going to be some challenges.”

The engine OEMs will determine whether or not they trust ultra low-viscosity oils in their older engines.

Even so, fleets may want to transition to the lighter-weight engine oils as soon as they’re able. Testing Shell has conducted in controlled environments and on the highway, makes a compelling case for low-vis oils. Arcy said Shell has gone to great lengths to ensure its test results reflect real-world conditions.

“You can structure a test to make your fuel economy look extremely good, but it may not be relevant,” he said of some testing methods employed today.

In one test conducted by Shell, five Class 7 straight trucks were run in a closed track environment. Trucks running 15W-40 were compared to those using Rotella T5 10W-30 oil. More than 400 sample points were taken, with the lighter-weight oil coming out on top to the tune of 1.6% in improved fuel economy.

Another test of Class 7 trucks in real-world conditions making local deliveries in Houston, Texas found the trucks achieved 3.3% greater fuel economy when running 10W-30 oil, compared to 15W-40. (All 10 trucks in this study alternated between 15W-40 and 10W-30 oils, to achieve credible results).

And a test Schneider National conducted using on-highway Class 8 tractors yielded a 1.57% improvement in real-world driving conditions when running 10W-30 oil. This test was conducted using the highly respected SAE J1321 testing protocol.

With the PC-11 category on the horizon, the opportunity exists to provide even greater fuel savings, Arcy said. Shell started testing the new category even before it was completed, developing an experimental 10W-30 oil with an HTHS of 3.0 cP (compared to the currently available 10W-30, which has an HTHS of 3.5 cP).

The initial tests of the experimental PC-11 oil revealed no compromise in protection. But perhaps even more promising were the fuel economy results. Five trucks were placed into team operations with a US fleet and four of the five showed fuel economy improvements when running the experimental PC-11 10W-30 oil, Arcy said. The best result was an improvement from 6.52 mpg using the currently available 10W-30, to 6.97 mpg running the PC-11 spec’ oil.

However, Arcy admitted the test was set up to evaluate durability, not fuel economy, and therefore he’s reticent to make any promises based on those early findings. Still, “When you look at this data, there’s definitely a fuel economy benefit there,” Arcy said.