If an engine oil formulator wants to move between base oil suppliers-to sidestep a shortage, solve a logistics snag or simply capture a better price-there are rules that allow a swap of one base stock for an equivalent one. The trick is to assure that the base oils really are equivalent, and the revised formulation delivers the same performance as the original API-licensed product.
One could simply say run all the tests for each base oil adjustment, but doing so would be costly and time consuming. Take, for example, the new Volvo/Mack T-13 engine test for oil oxidation, required for API CK-4 heavy duty diesel oils. It costs $175,000 to run, and oils must pass that and eight more engine tests to earn a license. Estimates are that a complete program for one formulation (one additive package in one base stock slate) can cost up to $1.5 million. Since almost all candidate oil test programs are run by additive suppliers, additive prices would have to cover these program costs.
Fortunately, the lubricants industry has generated reams of engine testing data to support trade-outs of many base stocks, which make it unnecessary to repeat every single engine test. That is, except for API Group III base oils. Their interchange data is more limited and formulators need to march through a battery of engine tests before making most switches.
Group IIIs were exotic 30 years ago, but at least two dozen refineries make them now and their ranks are swelling each year. The mature markets of North America and Europe are expected to continue to demand significant Group III volumes in the future, (including the ultra-high-viscosity-index types marketed as Group III+) for use where thinner viscosity grades become a primary requirement to meet challenging fuel economy requirements.
While more Group III is going into engine oils, blenders remain bound by interchange rules found in the American Petroleum Institutes Document 1509, the Engine Oil Licensing and Certification System. This document describes the development of engine oil categories for both heavy-duty and light-duty vehicles. Referenced worldwide, API 1509 is designed to define, certify and monitor engine oil performance, as demanded by vehicle and engine manufacturers.
A key part of the document is Annex E, which addresses Base Oil Interchange. BOI can allow additive suppliers and oil marketers to economize on engine testing in many cases. Annex E also defines the well-known API Groups according to their chemical and physical properties. Groups I, II and III are paraffinic mineral oils, Group IV is strictly reserved for polyalphaolefins, and Group V covers everything else including naphthenics, esters, polybutenes, etc. (See table below.)
How did 1509 and these Groups come about? Larry Kuntschik of Lubrication Solutions in Texas points back to the late 1980s, when he worked for Texaco. He relates how oil and auto companies held a series of meetings to hammer out a new engine oil licensing system-with hammer an apt word. The highly divided discussions finally ended, as positions like over my dead body blew the idea of any possible agreement apart, he says. Auto manufacturers, who had banded together as the International Lubricants Standardization and Approvals Committee (ILSAC), were adamant about the kind of licensing system they wanted, while API members felt it was important to at least try to get some kind of compromise to keep the API system alive.
Mike McMillan of MLM Consulting Services in Michigan, who was General Motors longtime representative to ILSAC, confirms this lack of harmony. The reason ILSAC was formed back in 1987 was because the OEMs were unhappy with the [oil development] system, he says. ILSACs vision was to create a worldwide oil classification and approval system in which the OEMs had significantly more input and control. First the automakers asked the oil industry for input, and then, between 1988 and 1991, they went on to develop a comprehensive draft of such a system entitled the North American Lubricant Standardization and Approval System, or NALSAS for short.
To say that the oil and additive companies were not pleased with NALSAS would be a gross understatement, McMillan says. NALSAS was never implemented, for a number of reasons. But in April 1991, the automakers offered a compromise proposal which included a number of conditions (many regarding engine test oversight and protocols) which had to be met if they were to withdraw NALSAS.
API agreed in principle, and thus began the process of creating todays Engine Oil Licensing and Certification System, remembers Florida-based Earl Hap Thompson of Global Standards Development Associates, who was on the API staff at the time. It took another year of intensive meetings to put meat on the bones of the new proposal, he recalls, but the final draft was published on April 20, 1992, and EOLCS formally launched in January 1993.
The backbone of the new licensing system was the additive companies offer to create a Code of Practice to register and monitor all engine tests, under the aegis of the Chemical Manufacturers Association (now the American Chemistry Council). Oil marketers agreed in principle, too, but balked at having to repeat every engine test for reasonable adjustments, such as a change in the viscosity grade. (As Kuntschik puts it, The OEM approach resulted in too much engine testing.) The answer was to group base oils by their chemical and physical properties to facilitate interchange and viscosity read-across.
Once the task group agreed on the concept of interchange, technical groups from auto, oil and additive companies contributed to the development of the various viscosity grade read-across guidelines, says Kuntschik. The read-across only applied to a few select tests, but it was a start. The task force also drew up four base oil Groups-one fewer than today. At the time we were only considering Groups I and II because that was what was in the market at the time. Basically, the differences boiled down to V.I., saturates and sulfur so that is what was used.
The Base Oil Interchangeability Task Force met in October 1991, and again four months later, relates Hap Thompson. Realizing that very high V.I. hydrocracked base stocks needed their own category, the task force added a definition for Group III, put PAO into Group IV and tossed everything else into Group V.
These new API Groups and interchange were beneficial to oil and additive companies, but as Mike McMillan comments, the OEMs had no part in creating the final base oil interchange or viscosity grade read-across guidelines that were implemented. Two [auto] representatives did attend the first several meetings of the group developing the guidelines, but they were non-voting participants, and ultimately stopped attending primarily because they felt their input to the group was being ignored, McMillan says.
Since that time, the oil and additive companies have been responsible for making interchange work-and pay millions to prove it with intensive matrix testing. Even so, according to Mike Brown, vice president, technology for SK Lubricants in New Jersey, some OEMs dont accept API/ATIEL BOI rules for granting approvals because they know the BOI rules dont protect their engines from borderline performing oils.
Today the range of Group III base oil producers is broader than ever before, Brown observes. From a handful of European and South Korean refiners 20 years ago, the players now include Abu Dhabi, Russia, Serbia, China, Qatar, Malaysia and diverse others.
We know of many different processes to get to the 120 V.I. minimum, 90 percent saturates minimum, under 300 ppm sulfur. Some major processes are Fisher-Tropsch slack wax isomerization, hydrocracker unconverted oil, and severe lube hydroprocessing, he says. These produce quite different base stocks from a compositional aspect. All of these can claim to be top-tier Group III or III+, with high V.I., nil sulfur and 99+ percent saturates, says Brown, but he questions if they are truly interchangeable.
Because they can differ in feedstock, process type and physical characteristics, he also wonders how interchange guidelines modeled on one or two Group III stocks (such as SKs Yubase from South Korea or Shells gas-to-liquids Group III from Qatar) can be applied across the Group III spectrum.
In North America, there is continued discussion about Group III interchange. According to industry sources, the cost to develop a data set allowing for interchange between differing Group III sources would run into the millions of dollars for each engine sequence test. The issue of who would fund such a program is another major question, with no one stepping forward at this point to commit the necessary funds. No matrix funds were made available for API CK-4s two new heavy duty engine tests (the Mack T-13 and the COAT) nor for the ILSAC GF-6 engine tests now being developed. Not surprisingly, established Group III suppliers are reluctant to fund matrix tests if it means sharing data with newcomers who want a fast track to approvals.
The long-term projections for Group III base stocks indicate that the market will grow. Passenger car engine oils are currently driven by SAE 5W-30 and 0W-20. However, lower viscosities such as SAE 0W-16 are on the horizon. Honda is currently specifying SAE 0W-16 for some markets, and factory filling with formulations as low as 0W-8. While other OEMs are skittish about such low-vis oils, the fuel economy advantages are very tempting.
On the heavy-duty side, the API FA-4 category, introduced on Dec. 1, has reduced HTHS viscosity requirements by about 15 percent, to a minimum of 2.9 centiPoise for SAE 30 weights. Already, engine oils with HTHS of 2.6 cP (for SAE 20) are being tested in North America, while Europes Iveco is using 2.6 cP engine oils for factory fill. There has even been some test work at 2.1 cP (SAE 12). In order to meet these very low viscosities and maintain volatility, greater amounts of Group III base stocks will be required.
Base oil interchange is a valuable tool for engine oil testing and product development. Without it, there would be far fewer choices in engine oils, less flexibility and much greater costs. Joan Evans, global industry liaison manager at Infineum in New Jersey, believes that the industry needs to continue to bring forward data to help define appropriate BOI/VGRA guidelines.
Even so, its possible that the base stock groups as we know them now may be reaching the end of their usefulness as a basis for robust interchange.
The Impetus for Interchange
Why do we need interchange at all? It helps to understand how a new oil development program is executed by additive suppliers and oil blenders. Much of it depends on the size of the business opportunity. For major oil marketers, oils are blended at multiple locations. Inherent in that process is the fact that each blending location may use a different base stock slate for their products. One blend plant could have a lower V.I. base stock mix than another. In order for an additive supplier to successfully supply formulations that perform in the broadest market, they typically develop data in the lowest V.I. base stocks and then translate that into demonstrated additive performance for all plants.
So two things occur. First, testing begins very early, often before the final details of a new category are determined. That leaves the very real possibility that a change in test limits or test procedures could occur which would make the prior work useless. Second, the fewer the tests that need to be run, the better from a timing and cost view.
When examined in detail, BOI directs the schedule for an engine test program and is an important indicator of which tests may be critical to the successful completion of the program. Some of the guidelines are quite simple. For instance, engine testing is not required when a single interchange base stock that meets the definition of Group I, II, III or IV is used at less than or equal to 10 percent (by mass) of the blended engine oil formulation. Some provisions for Group III and Group IV allow even higher percentages without further engine testing. Always, any blend with base stock substitutions must meet the physical and chemical requirements of the claimed category. -Steve Swedberg