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Automotive Lubricants

How About Another Engine Test?

As you all know, I think we may overdo the engine test requirements for engine oils. I’ve long advocated for consolidating some of the current tests into one that measures more parameters. I suspect that there are many oil and additive companies that support that position. I also know that the original equipment manufacturers feel that their engine is the only one that can measure the relevant parameter. For example, there are currently five different wear tests in API CK-4 and FA-4. Ford has approached the API Diesel Engine Oil Advisory Panel with a request to add another wear test to the mix.

We already have a total of nine engine tests for this API category. Surely no one wants to add another test. How did we get to this point, and where do we go from here? Let’s take a long look at this situation and maybe see an idea or two.

Ford’s diesel engine is a 6.7L V-8 with four valves per cylinder. It was introduced in 2011. While the engine has earned some good reviews and performs well, Ford believes it may have some wear problems. They approached the DEOAP about the addition of an engine test designed to evaluate the wear issues. DEOAP was unable to agree on whether to recommend this action to the Lubricants Standards Group. Ford went directly to the LSG with the request that the Ford 6.7L Diesel wear test be added to API CK-4 as an additional test and add the designation PLUS to those oils meeting the Ford test. As was the case with the DEOAP, the LSG could not reach a decision and has decided to ballot the group to confirm its position.

This issue has positives and negatives. Ford has tested many oils and has determined that some current CK-4 products do not meet their minimum requirements. Apparently, some of the oils were deficient in the proper anti-wear components, namely zinc dialkyldithiophosphate.

The same test had come during the development of CK-4 and was related to the “Universal” oil application issue. For those not aware of this, most fleets have a mixture of diesel- and gasoline-fueled engines. Shop inventory practices are such that one oil is preferred over two or more because of possible misapplication. CK-4 specifically states that for a claim to be made of API SP, all specifications for both categories must be met. That means the phosphorus level must be 0.08 wt% max to satisfy SP.

CK-4 is more generous with a 0.12 wt% max limit. Ford’s 6.7L engine seems to need the higher level of phosphorus, so the company would not be agreeable with a universal oil for customers using its engines. Ford has apparently been satisfied with recommended oils, including its own oil, WSS-M2C171-F1. It sees 0.10 wt% phosphorus as a safe level and recommends that as the minimum for its engines.


So, what’s the solution?

Ford is trying to get away from a chemical limit and instead have a test to confirm acceptable performance. The DEOAP and LSG are dubious of another test, and the users are caught in the middle. Of the current wear tests, two are in Cummins architecture, one is a very old test based on early roller follower designs (GM RFWT), the fourth is a ring and liner wear test using a Volvo/Mack engine and the fifth is a single-cylinder, laboratory engine test using Caterpillar hardware. Perhaps the Ford test will predict the same performance as one of the current tests. PC-12—which is in the formative stages of development—is looking for fewer tests to predict wear protection. The Ford engine should be included in that evaluation.

As if PC-12 and CK-4 PLUS aren’t enough, API SP/GF-6 is in discussions about an additional test. Again, Ford is promoting this issue. Ford was the driving force behind the Sequence IX (low-speed pre-ignition test). The Sequence IX, often referred to as the LSPI, measures the impact of the engine oil on pre-ignition in direct injection, gasoline-fueled engines, particularly those that are turbocharged.

Gasoline engines run on the principle that the fuel should burn quickly. This provides the most power for the vehicle. Depending on the compression level (compression ratio), more useable power can be developed. The limit to this is whether the fuel can ignite properly.

Pre-ignition is the technical term for engine knock. Knock is the result of something causing the engine cylinder to fire before it is supposed to do so. One of the causes is a fuel with lower than required octane. If the number is too low, it will burn too early in the cycle. It can be a slight sound (trace knock), or it can be more pronounced. That can range from a rumble to destruction!

Today’s smaller engines—for example, 1.5L DITC gasoline-fueled—can deliver impressive amounts of power. As a gauge of power output, engines are often rated by the horsepower per cubic inch. The engine in my first car, a 1957 Chevy with 283-cubic inch displacement, delivered about 150 HP. That’s 0.5 HP/cubic inch. Gas mileage was about 15 miles per gallon. My current set of wheels, a 2020 Honda Pilot with a 3.5L (213-cubic inch) V-6 delivers 280 HP. That is 1.3 HP/cubic inch. Gas mileage is about 26 mpg, although the sticker says 22 mpg.


More power can be gained by turbocharging an engine. The concept is that forcing more air into the cylinder means you can add more fuel to keep the fuel-to-air ratio where it is most efficient. Fuel economy is better, and the corollary emissions are lower. Lots of pluses for that configuration.

There is one drawback with turbocharging, though: Minute amounts of oil leak from the bearings supporting the compressor fan. Although the amount is small, the very hot surfaces in the cylinder turn the oil into a deposit that gets and stays hot. That hotspot causes the pre-ignition to occur. Oil dilution can also add to the deposit-forming tendencies.

The Sequence IX is a test using a Ford 1.5L turbocharged, DITC gasoline-fueled engine. Using new test oil, the engine is run through an operational cycle, and knock occurrences are counted. The number is a very small one, so any knocking will fail the oil. So far, so good. The International Lubricant Specification Advisory Committee, which speaks for the auto industry, has recommended that the Sequence IX be run on aged (used) engine oil.

Several automakers formally requested that the American Petroleum Institute’s Lubricants Group develop a supplement to the API SP light-duty engine oil specification, asking to add a test of aged oil protection against damage from low-speed pre-ignition. Their Aug. 18 letter from Ford Motor Co.’s Michael Deegan, chairman of ILSAC, stated, “We request that the supplement include all the performance requirements presently in API SP, plus the requirements of meeting the limits set for the aged oil LSPI performance of a lubricant.”

Deegan noted that API SN Plus, API SP and ILSAC GF-6 specifications address a lubricant’s ability to protect turbocharged engines with gasoline direct-injection from low-speed pre-ignition when the oil is fresh. But he stated that “further protection is now necessary to prevent equipment failure which may be connected to a degradation in the Sequence IX protection of the lubricant over its standard oil drain interval.”   In fact, published studies have documented that the potential for damage from low-speed pre-ignition increases as the engine oil ages.

Of course, Ford has test data on this variation. It has even developed a protocol to age the oil under standardized conditions. While it’s not clear to me whether the passing limits will be the same or if there will be modified limits. I’m also not clear whether this version (used oil) of Sequence IX is intended to replace the current new oil version.

Historically, engine test development has originated in the OEMs’ house. They’ve got the hardware and the problems to address. When they think they have a test, they bring it to the industry and ask that the test be included in a category. Often, they have already included the test in their own specifications, so the oil marketers and additive suppliers scramble to meet the new test and/or limits.

ASTM is tasked with standardizing the test procedure and developing the test limits, along with finding and adding the proper reference oils. Finally, API develops user language, sets the category limits and introduces the new category. Not surprisingly, the membership of API, ASTM, ACC and ILSAC overlap significantly. That’s good, since the issues related to the test development are discussed by all in different settings. Technology, marketing and chemistry are all included.

I think there could be ways to streamline the process, but it will require some transparency to achieve meaningful improvements. One thing I do know is that both these test developments and inclusion in existing categories is time consuming and costly. My best guess for the 6.7L test is that it will be included in PC-12, scheduled to be introduced in 2026 or 2027. Since PC-12 will likely have some new tests, it should be fairly smooth. The Sequence IX change, if accepted, will be much more awkward. In any event, the cost could be pretty large.

My sources tell me that the PC-11 development cost the industry about $350 million. The recently completed API SP/GF-6 introduction came in north of $400 million. Combined, we’re looking at about three quarters of a billion dollars! It’s beginning to sound like a government project. Let’s hope it isn’t.