Oil Additives: The Untold Story

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Fleet Owner  /  April 7, 2016

Lubricant makers aim for the “Goldilocks solution” when it comes to the right engine oil additive mix

If you wonder about the purpose of all the chemical additives blended into truck engine oils—especially the new PC-11 formulations coming to market this December—it helps to think about barbecue sauce.

Barbecue sauce?

“Think about the spices that get added to barbecue sauce to create a specific flavor,” explains Dan Arcy, OEM technical manager for Shell Lubricants.

He says such spices—cayenne pepper, honey, Worcestershire sauce, and prepared mustard, just to name a few—need to be added in just the right amounts and at just the right time in the sauce-making process so they don’t overwhelm each other in terms of flavor. Those formulations also take into account what kinds of meats they’ll be used with, as well as the heat levels of the particular cooking procedure involved, Arcy notes.
A similar brand of thinking occurs when blending chemical additives into engine oils, an effort he calls aiming for the “Goldilocks solution,” to ensure the additives balance one another in terms of their properties.

“You’ve got detergents, dispersants, corrosion inhibitors, anti-wear chemicals, and viscosity modifiers among the many additives in the PC-11 engine oil blends,” he points out. “And we’re trying to balance them for specific purposes.”

Gary Parsons, global OEM and industry liaison manager for Chevron Oronite Co., emphasizes that fully formulated engine oil—one containing specific additives—serves four primary purposes:

- It lubricates by keeping metal surfaces within the engine from coming into contact with one another.

- It cools engine components.

- It removes or neutralizes combustion by-products and contaminants from the engine.

- It prevents oil degradation due to oxidation, which is the absorption of oxygen. 

“Additives play a major role in each of these performance areas,” Parsons says.

Additive classifications include anti­oxidants, detergents, dispersants, anti-­wear compounds, friction modifiers, pour point depressants, antifoam, viscosity modifiers, and seal swell agents, he explains. During the development of engine oil, formulators optimize performance by carefully balancing the treat rates and performance of each component.  

“In the case of PC-11, the finished oil must be capable of passing 11 standard industry engine tests and six bench tests, all evaluating various aspects of engine oil performance,” Parsons notes. “In addition to the engine and bench tests, additive companies and lubricant suppliers also run extensive field trials to test the performance of oil formulations under a wide variety of conditions over millions of miles.”  

Marvin Kerkstra, manager of lubricants technology for Citgo, says that “finished” heavy-duty truck engine oil is typically comprised of 85% to 90% base oil, with the remaining balance made up of a concentration of chemical additives.

“The additives provide several benefits, including keeping the engine clean by controlling deposit and sludge formation, providing wear protection, and preventing corrosion and oil aeration,” he explains. “The antioxidants help control oil breakdown or varnish formation resulting from sustained high engine operating temperatures.”

Mark Betner, Citgo’s heavy-duty product line manager, points out that PC-11 oils will use more advanced additive technology designed to reduce oil oxidation by up to 60%, provide greater wear protection, and reduce the tendency for oil aeration.

“Since newer diesel engines tend to break down multi-viscosity oils more rapidly due to design, PC-11 engine oils will provide greater viscosity shear stability, which means they have greater high temperature viscosity retention or resistance to viscosity breakdown due to viscosity shear,” he notes.

Parsons adds that PC-11 is actually a category that will contain two distinct engine oils:

- A conventional viscosity grade of oil, which will supersede CJ-4 and be commercialized as CK-4; and

- A lower viscosity or thinner oil that will be commercialized as FA-4 and may not be backward compatible. 

“Each [truck and engine] OEM is anticipated to offer guidance on which model-year engines the oils can be used,” Parsons points out. “From a performance standpoint, CK-4 and FA-4 oils will pass all of the tests mentioned above. [But] depending on the additive supplier and formulations involved, some oils may contain new additives,   and others may contain different combinations of existing additives.”

Friction modifiers, for example, will be used to help improve fuel economy while maintaining the wear performance of the oil. “In the case of the thinner FA-4 oils, supplemental wear inhibitors may be necessary to provide wear performance with thinner oil films,” he notes.

Brian Humphrey, OEM technical liaison-HD driveline for Petro-Canada Lubricants, adds that while lower viscosity oils are beneficial for improving fuel economy, there is concern thinner oils may not sufficiently keep engine surfaces separate to prevent wear due to rubbing.

“Sufficient anti-wear compounds or other forms of chemical surface protection must be included in the oil,” he stresses. 

“All oils must be tested and certified for additive compatibility and long-term stability, no matter what base oils or additives are used,” Humphrey explains. “While synthetic oils may often use the same additive system as mineral oils, it may be desirable to use a specific additive package that takes maximum advantage of synthetic oil properties to create an even higher performance product.”

In his view, lubricant formulation is a balance, and more additives don’t necessarily make engine oil better.

“Each additive has different attributes and can impact the performance of oil,” Humphrey says. “It’s finding the right balance that is key. Of course, there are additives that may not be fit for purpose on their own but may provide benefits when used in a properly formulated lubricant.”

No DIY

Engine oil experts also strongly caution against engaging in a “do-it-yourself” additives strategy since after­market chemical additive packages may be fine on their own, but they can throw off the “careful balance” of fully formulated engine oils, especially where PC-11 is concerned.

“For example, fully formulated engine oil contains detergents and anti-­wear compounds,” explains Parsons. “The anti-wear component works by attaching to the surface [while] the detergent wants to keep the surface clean. That’s why [engine oil] formulators strike a careful balance between the detergent and anti-wear [additives] to make certain the anti-wear can do its job without interference from the detergent. That’s also why the use of a supplemental additive could potentially throw off that balance and actually lead to problems.”

Citgo’s Kerkstra agrees with that view. “Most major engine manufacturers do not recommend adding additional additives to engine oil,” he says. “Think of it this way: If we get a prescription from our doctor, do we go to the pharmacy and grab an off-the-shelf medication to add to our prescription thinking that we will improve the prescription? Most likely we’ll end up with bad results by thinking that we know more than the doctor and pharmacist.”

Another consideration is that engine oils are licensed by the American Petroleum Institute based on their specific formulation.

“When aftermarket additives are added to that engine oil, the original oil formula has been altered, which results in that engine oil no longer being representative of the oil that was manufactured,” Kerkstra emphasizes. “If for any reason there is an engine warranty dispute involving a lubrication-related failure, the equipment owner’s warranty for both the engine and the engine oil could be denied.”

More isn’t better

Lastly, “more is not better,” he stresses, so attempting to add any aftermarket additive to the engine oil can result in poor engine startup lubrication or even promote greater engine deposits since the aftermarket additive may not be compatible with the original engine oil formula.

As always, the primary recommendation is to use the engine oil that’s approved and suggested in a vehicle’s operating manual, Petro-Canada’s Humphrey notes.

“What makes PC-11 special is that these products are the culmination of considerable research into lowering viscosity while maintaining their ability to withstand a high-shear engine environment.

[This means] that although thinner, especially with the FA-4 tier but not with the CK-4 tier, they are stronger and may require fewer regular oil changes [as they] provide engine protection for longer periods,” Humphrey says. ”The opportunity for extending drain intervals will exist, but it will have to be proven viable for each fleet.”   

The final lap for PC-11

With the first licensing date  for the new PC-11 truck engine oil standard still officially pegged for Dec. 1 of this year, Shawn Whitacre, senior staff engineer of engine oil technology for Chevron Lubricants, says by now most formulations are “locked in” and awaiting final results from various OEM-specific bench tests.

“To have products ready for Dec. 1, testing needs to be wrapped up by April or May,” he explains.

One last avenue being pursued by several lubricant makers is crafting PC-11 oils that can be used in both diesel and gasoline truck engines.

“That’s more challenging because of the phosphorus limits due to the three-way catalysts used in gasoline engines,” which are 33% lower compared to diesel engines, Whitacre points out.

“The flexibility regarding phosphorus limits goes away” when lubricant makers seek to craft such dual-performance oils, he stresses. “That also forces you to use more additive chemistry.”

Whitacre, who also serves as chairman for the American Society for Testing and Materials heavy-duty engine oil classification panel tasked with the final development of PC-11 oil requirements, stresses that only one of the two PC-11 blends being developed—CK-4, a 10W-30 blend—will be considered backward compatible.

“CK-4 will be able to claim compatibility with older 15W-40 specifications in terms of viscosity,” he says. CK-4 oils will be approved for use in many of the same engines and applications that currently recommend CJ-4.

The second PC-11 oil blend (FA-4), however, is of a thinner viscosity than CK-4 and won’t be as backward compatible.

“FA-4 will be at a lower viscosity level than today’s oils, offering more optimized fuel economy for engines that are designed to use these thinner oils,” Whitacre notes. “Like with other low viscosity oils, we don’t expect that engine makers will allow these oils across the board.”

He said it seems that OEMs are still working on their own engine test programs at this point to determine to what extent the new FA-4 oils can be recommended—if at all.  Other issues to note include the following:

- Now that the “rules of the game” are officially established, the lubrication industry effectively goes into a commercialization phase for CK-4 and FA-4.

- Both PC-11 oils will be formulated to be more resistant to oxidation, meaning that they can stand up to elevated temperatures for longer periods of time without breaking down. “This is something that engine makers identified as a priority because of the greater demands that new engines are placing on the oil and because engine makers continue to push for longer oil change intervals,” Whitacre notes.

- Engines need to be specifically designed to operate with thinner oils, especially the FA-4 blend, which is why the new PC-11 oils may not meet all the lubricant specs established for some older engine models.