Universal engine oils, crafted to serve gasoline and diesel fueled vehicles alike, have been a mainstay of the lubricants market for decades. Some believe the rollout of the new API CK-4 and FA-4 heavy duty engine oil categories this month will close the door on these products-but others insist theres still intelligent life in the universal.
The idea of a mixed-fleet, universal engine oil emerged in the 1970s, when commercial fleet operators found it appealing to carry a single product that could serve both gasoline and diesel engines without fear of misapplication. In this, they were following the lead of the U.S. Army, which had a specification for universal oils as early as 1964. The American Petroleum Institute helped out by allowing qualified products to show both C (heavy duty) and S (light duty) categories in the API Donut logo-always with the heavy duty category first, as in API CD/SE or API CD/SF.
By the 1990s, the automakers top concerns were tailpipe emissions and fuel economy, ILSAC GF-1 gasoline engine oils had appeared in the market, and API CH-4 diesel engine oils were moving into place. It was at this point that some passenger car OEMs started lobbying against universal oils. They feared that the high levels of phosphorus additives allowed in heavy duty diesel oils would damage their exhaust system catalysts.
Still, API continued to make allowances for licensing universal oils. Depending on the S category being claimed, diesel oil marketers could waive or modify various gasoline test procedures. A footnote in API Document 1509, the rulebook for engine oil licensing, shows how it was done until recently:
For all viscosity grades: If CH-4, CI-4 and/or CJ-4 categories precede the S category and there is no API Certification Mark, the S category limits for phosphorus, sulfur, and the TEOST MHT do not apply. However, the CJ-4 limits for phosphorus and sulfur do apply for CJ-4 oils. Note that these C category oils have been formulated primarily for diesel engines and may not provide all of the performance requirements consistent with vehicle manufacturers recommendations for gasoline-fueled engines.
Similar provisions were made for API SM, SL and SJ oils-but that window was nailed shut for API CK-4 and FA-4. This footnote cannot be applied if CK-4 or FA-4 is claimed, the rulebook now states. If a universal oil wants to claim CK-4 and FA-4, it must also meet all requirements of the active API S categories. When API SP is introduced sometime in 2018, it undoubtedly will have the same full coverage.
Plugging the Gap
The implications are many and varied. First, there is the question of how such products are received by automotive OEMs. ILSAC-the auto industrys International Lubricants Standardization & Advisory Committee, which primarily is concerned with gasoline engines-has taken the position that, if all requirements are met, such oils are satisfactory for use. Always, ILSAC favors products meeting its own GF-series specification or APIs Resource Conserving designation.
For heavy duty engine manufacturers, the universal oil concept is less troublesome. According to Greg Braziunas, manager of oil and coolant systems at Daimler Trucks North America, The S claim is mainly related to the phosphorus level of the oil. As a global engine manufacturer, Daimler already has extensive experience with 0.08 percent phosphorus oils. We have reached the conclusion that trying to boil down performance of an oil to one level of one component is simply not representative. Rather, we judge an oils merit not based on its chemical makeup but rather its performance in both industry standard and Daimler internal testing.
That highlights another question: With phosphorus limited to only 0.08 percent for the SN side of the equation, can a universal oil still successfully offer wear protection on the heavy duty side?
According to one additive supplier, a fresh approach is needed to secure CK-4/SN or FA-4/SN performance, especially in the lighter viscosity grades. Whenever you reduce something core to the formulation like zinc dialkyl dithiophosphate (the antiwear agent that is the main source of phosphorus) you have to replace that functionality by other means.
In a webinar for Fleet Equipment magazine, Keith Corkwell, Lubrizols global business manager for heavy duty engine oil additives, noted that the emphasis on fuel economy and emissions which led to CK-4 and especially FA-4, is driving changes in oil formulations. Hardware changes such as increased in-cylinder pressure, higher thermal loading and down-speeding of engines to run at lower speed/higher torque, also demand new chemistries to enhance engine protection and deliver fuel efficiency.
When you add to that the quest for a universal oil, there is no doubt that things must change. Engine oils are a complex of base oil, additives (typically supplied in an additive package), and viscosity modifiers. Generally, base oil represents over 80 percent of the finished product, with additive packages and viscosity index improvers making up the rest.
Much of the current focus in HDEO is on improving fuel economy through viscometrics. Corkwell noted how simply reducing the high temperature, high shear rate viscosity of the oil can have a positive effect on fuel economy. As HTHS viscosity drops, fuel economy improves, he said. Just changing from a standard API CK-4 SAE 15W-40 to a 5W-30 may be worth as much as 1.5 percent fuel economy improvement-and a further move to the lighter FA-4 5W-30 can bring almost 1 percent more.
Formulating true universal oils that meet both diesel and gasoline performance requirements is a large challenge, Corkwell added. The formulation not only has to pass all tests of both specifications, but also has to conform to tighter chemical limits.
The good news, he continued, is that this is technically feasible thanks to novel chemistries developed in the decade since the API CJ-4 category was introduced. Non-metal-ash based antiwear components coupled with a holistic formulation style can enable improved fuel economy and enhanced wear and oxidation protection at the same time-even at lower phosphorus limits-and also allow some API CK-4 and FA-4 products to meet SN requirements.
All of that creates an opportunity for an ongoing universal SAE 5W-30 engine oil. But there is always a caveat: With low viscosity comes its evil twin, higher volatility.
Both CK-4 and SN have Noack volatility restrictions which dictate the type of base oil which can be used. For API SN the volatility limit is 15 percent; for CK-4 its 13 percent.
Bob Salgueiro, industry liaison advisor at Infineum, points out that base stock selection is critical to viscosity grade. SAE 10W-30 may be formulated to satisfy either CK-4/SN or FA-4/SN and still use mostly API Group II base oil, with the addition of some Group II+ or Group III to meet NOACK volatility. SAE 5W-30 can also be formulated to satisfy those claims, he said, but likely will require Group III with some Group III+ or Group IV (polyalphaolefin) to achieve volatility and low temperature performance limits.
Conventional base stocks, however, including some API Group II and II+, will have trouble meeting the stringent volatility limits of SAE 5W-30 universal oils. The answer is to select Group III and Group IV base stocks which have volatilities in the 13 percent Noack range, and viscosities of about 4 cSt at 100 degrees C.
Not only does the base stock need to be very low in volatility, but the additive package also must meet similar limits. This could require some operational adjustments, primarily in the use of diluent oils which meet or are close to the same volatility limits.
In his webinar, Lubrizols Corkwell summed it up succinctly: Formulating true universal oils that meet both diesel and gasoline performance requirements is possible, but challenging. This is accomplished through the additive package and performance polymers. Base oils are a key ingredient and we see increased use of Group III base oils in lighter viscosity grades. But there is no link between phosphorus level and base oil requirements.
Whos In?
Some oil marketers are more than willing to go with universal oils, given the continuing demand. The two largest U.S. marketers of commercial lubricants have both announced they will offer fully compliant API CK-4/SN universal oils on Dec. 1, 2016.
Shell will have Shell Rotella T6 Multi-Vehicle 5W-30, a full synthetic meeting both API CK-4 for diesels and SN for gasoline engines. Matt Urbanak, primary formulator for Shells Rotella T product line, noted that field testing is the real proof of its performance. One of Shells field-test engines (a Detroit DD15 with 475 horse power) achieved fuel economy in a Freightliner Cascadia of about 6.3 mpg with extended 55,000-mile drain intervals. When it was disassembled in San Antonio, Texas, after 800,000 miles, Urbanak said, the engines internal health gave the company confidence that it could offer backwards compatibility with the oil.
Keith Selby, the companys global technical manager for heavy duty engine oils, said this universal SAE 5W-30 could deliver up to 2 percent better fuel economy-but the greatest challenge is convincing fleets and owner-operators they can attain such fuel savings without compromising on wear protection.
Chevron, too, is introducing an SAE 5W-30 CK-4/SN product this month. Delo 400 XSP SAE 5W-30 will replace Delo 400 LE Synthetic SAE CJ-4/SN. According to Shawn Whitacre, senior staff engineer, engine oil technology, Within the Delo family of HDMOs, all of our current products meet both C and S claims. Nothing is changing.
Chevron said in a statement that the Delo 400 product line has gone through one of the most rigorous, varied and exhaustive field testing programs in Chevron history. We are seeing some of the longest drain intervals and best engine protection in our company history, due to our industry leading formulation expertise, declared Len Badal, global brand manager for Chevron Delo. Chevron is currently field testing the new Delo products in more than 900 engines, across a range of OEMs.
Others are still eyeing the universal possibilities. Phillips 66 Lubricants, for example, gives them a hopeful thumbs-up. Our position on universal oils is that both the Phillips 66 and the Kendall Motor Oil brands will offer a balanced portfolio with both diesel-only and universal products, director of marketer products Tony Negri told LubesnGreases. Universal oils will be available primarily in the market general and full-synthetic tiers.
In general, we see the need for universal oils to be on the decline, Negri added. However, we will continue to monitor the marketplace and listen to our distributor network to stay abreast of all trends.
Other majors are keeping mum, their eyes fixed firmly on CK-4 and FA-4 alone. Petro-Canada Lubricants, for example, is launching its Duron next generation API CK-4 and FA-4 products to the market on Dec. 1, and says they will be available in four performance tiers. However, a p.r. contact said the company could not confirm by press time whether a universal oil version will join that line up. Nor did an ExxonMobil representative respond to inquiries about whether Delvac has a universal up its sleeve.
What Users Want
The final piece of this puzzle is the end user. A number of major fleets have switched already to SAE 10W-30 CJ-4 engine oils to capture the fuel economy benefits.
According to Bob Salgueiro, SAE 5W-30 API FA-4/SN could be a true universal oil. But will end users be willing to pay a premium for a full synthetic oil? Infineums research suggests that large fleet owners put a value on engine oils that can be used in both old and new diesel engines-but they have less interest in seeing an API gasoline claim on the oil.
Theres still a market for universal oils in smaller fleets with mixed engine types. There is also need wherever stocking multiple oils is a problem, such as offshore. In any event, the technology to create universal oils is available. As Salgueiro concludes, the issue is cost versus benefit.