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I dont know if youve noticed, but in the arcane world of engine oil formulations and specifications, acronyms are the heart of many discussions. It is possible to write or speak entire sentences without benefit of many real words. Instead you could hear something like, We ran a VG for the GF-5 BOI in a 5W-30 for VGRA.

While this may sound pretty impenetrable to those who do not make a living in the industry, it is perfectly clear to oil and additive industry formulators. Even the organizations involved with engine oils go by their initials rather than names: API, ASTM, ACC, ILSAC and EMA, just to name a few.

What has evolved then is shorthand for many of the key activities which govern the development, testing and approval of engine oils. The hierarchy of this pyramid of capital letters starts with marketing organizations and engine manufacturers, who establish performance categories describing the requirements to be met in order to satisfactorily lubricate certain classes of engines. The tests necessary to prove this performance are developed by interested parties, who then pass them on to other organizations which establish passing limits on these tests. The thicket of acronyms becomes more dense still whenever the industry tackles a new engine oil upgrade. As work gets under way on the next diesel engine oil upgrade – PC-11, another acronym well be seeing lots more of – Ill try to translate a bit of it for you.

For engine oils in the United States, the American Petroleum Institute (API) sets the standards for approval through API Document 1509, the Engine Oil Licensing and Certification System (EOLCS). Within the pages of this document are the rules and minutiae necessary to gain approval for engine oils meeting any of the active API categories.

Document 1509 identifies the engine tests required and the passing test limits, as well as the process for an oils approval and any necessary paperwork. It is not strictly necessary to gain an API license to sell engine oils; its a voluntary system. But without a license you cannot display APIs trademarked Service Symbol (Donut) and Certification Mark (Starburst), indicators of measurable quality and proven performance.

Needless to say, the approval program by which a passenger car engine oil (PCEO) demonstrates that it meets a specification such as API SN Resource Conserving or ILSAC GF-5 is not inexpensive to achieve. These programs are typically run by the major additive companies, who work with the oil marketer to develop engine oils that meet industry standards and are cost effective to produce. The testing is usually done for a specific base-stock-and-viscosity-grade combination, with additional tests to cover other base stocks and viscosity grades as needed. Ill go into more depth later, but the two key acronyms to remember are Base Oil Interchange (BOI) and Viscosity Grade Read-Across (VGRA).

Engine testing is always a struggle. Should the formulator strive for a sure-fire test result (sometimes called fat packing) at a significant product cost, or go for a more cost-effective additive dosage that will be acceptable to the marketplace? To keep the playing field level, the Petroleum Additives Panel of the American Chemistry Council (ACC) maintains the Product Approval Code of Practice (the Code), which governs how engine test programs are run (see www.americanchemistry. com/paptg). The Code includes procedures for modifications to engine additive packages, which allows for test data that have been run on earlier versions of an additive to be acceptable for performance demonstration purposes, within very narrow, well-defined limits.

The Code was put in place 20 years ago to address the need to make test programs more cost effective, and also to make sure that programs were run in a standardized manner. ACC represents the additive industry, and one of its stated purposes was to provide more accurate performance results, there-by yielding more cost-effective engine testing – a mutual benefit both to lubricant formulators and their customers. In addition, the Code aims to improve communications between program sponsors (the additive companies) and customers (blenders) because standard practices are described in detail.

Engine oil test programs also depend on repeatability and reproducibility of engine tests. All test labs track the pass/test ratios of all engine tests they perform. There is a good reason for this, since a shift in test severity will show up over time as either more passes or more failures. Not surprisingly, given that an engine has hundreds of moving parts and is subject to a lot of variables, the pass/test ratio is typically less than 100 percent. And some tests are notoriously tricky to control. Just do the math on an engine test which has a pass/test ratio of 75 percent, and you can see that a large percentage of the results are likely to disappoint – prompting a rerun of the test. With engine tests often costing more than $50,000 each, youll also see that a candidate GF-5 engine oil program can cost far more than the sum total for one run of each engine test. In fact, its not unusual to budget as much as 150 percent of a programs once-through-each-test cost, just to cover those tests that dont pass the first time.

From the lubricants industrys point of view, one of the most important issues is how to gain the broadest possible coverage for an additive package, rather than require a completely new test program for every base stock. Governed by API 1509, Appendix E, this is referred to as Base Oil Interchange Guidelines, or BOI. BOI allows a blender some flexibility to switch among base stocks, without fear of compromising the finished products performance.

In the early days of engine oil testing, base stocks were considered to be essentially equivalent and differed only by viscosity – a pretty valid position given that most available base stocks were refined in the same manner. However, as testing became more sophisticated and new refining techniques emerged, it became all too clear that not all base stocks were created equal. The industry searched for ways to characterize base stocks without costly molecular analyses. One early attempt was called the n-d-M analysis; based on refractive index (n), density (d) and molecular weight (M), it gives some idea of what the base stock composition is like. However, n-d-M turned out to be a poor predictor of performance in engine tests.

The real turning point came in the 1980s when the first hydrocracked base stocks became widely available. Engine testing showed that these fluids responded differently to additive technology than traditional solvent-refined base stocks. After many trials it became apparent that, while hydrocracked base stocks offered some unique advantages, there were performance issues that needed attention.

API 1509 Appendix E describes a simple system to categorize base stocks using only three parameters, which the work with hydrocracked stocks showed to be of importance: viscosity index, sulfur content and saturates content. Using just these properties, API sorted base oils into Groups I, II, III and others, as shown in the chart below.

Appendix E specifies the conditions and tests required to allow BOI. In most cases, substituting less than 10 percent of one stock for another does not require additional engine testing. Blend studies and bench tests must still meet requirements.

For substitutions greater than 10 percent, the amount of engine testing required depends on the BOI desired. For instance if you want to substitute a Group II base stock for a Group I base stock in a passenger car engine oil formulation meeting GF-5, youll have to rerun the Sequence IIIGA and IIIGB tests for engine wear and oil thickening, as well as a Sequence VID test for fuel economy. So long as the viscometrics are correct (that is, equal to or greater than original viscosity) no Sequence IVA is required.

It would be nice if this held true for all combinations but sadly, it doesnt. In fact, the interchange system is very complex so in order to understand it you need to read the entire Appendix E, which is available on the API website (www.api.org/ certifications/engineoil/ pubs/index.cfm).

Lest you think that viscometrics is unimportant, I recommend that you also take a look at Appendix F of API 1509, the Viscosity Grade Read-Across Guidelines (VGRA). This covers the method for applying engine test data from one viscosity grade to another. An engine oil formulator chooses the most difficult viscosity grade for testing, and then uses that one test program (plus a few extra tests) to cover a wide range of additional viscosity grades.

As an example of VGRA in action lets take our GF-5 program and select the viscosity grade for testing which gives us the greatest number of viscosity grade reads. The formulation must adhere to ACC guidelines for additive treatment, viscometrics and so on.

In our example, SAE 5W-30 would be selected to gain the widest read-across coverage. Appendix F shows some watch outs based on test results in the Sequence VID and Sequence IIIG, and it shows that some of the bench tests (TEOST 33 and MHT4) will need to be rerun, too, depending on which additional viscosity grades we target. Of course, the BOI parameters also have to be met. As with BOI, in order to understand VGRA you must read through the entire Appendix F to fully grasp what is needed. This document is also available on the API website.

The heavy-duty engine oil side of the equation follows a similar pattern. HDEO tests are also base stock and viscosity sensitive, so BOI and VGRA are important parts of each program. The stakes are higher here though, since heavy-duty engine testing is typically more expensive than passenger car engine testing. The good news is that there arent as many viscosity grades of interest in HDEOs.

So theres a brief look at the wonderful world of North American automotive engine oil acronyms. Of course, the European system has its own set of groups, tests, documents and acronyms. Like many, I maintain a cheat sheet which puts names to this alphabet soup, and you should too, if youre going to track the who, what, when, where, why and how of this amazing business.

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