Market Topics

Automotive

Share

Ongoing work to improve oil performance has us looking to upgrade both the heavy-duty (PC-11) and passenger car (ILSAC GF-6/API SP?) engine oil standards for North America. To add to the fun, each of these proposed new categories is slated for introduction at about the same time, early to mid 2016.

Of course, performance is defined by both engine sequence tests and laboratory bench tests. And before these new oils can come to market, as many as 14 tests must be scrutinized to see if their limits should be reset or if new tests should be developed from scratch altogether. Obviously, that is a big mouthful for vehicle manufacturers, oil and additive suppliers, test laboratories and other interested parties to digest.

With so much at stake, this is a good time to review the process, not of any one test, but of how the industry arrives at a new test or test limits for its oil categories. To start, the process needs to cover certain essential steps:

What are the drivers for the test – why is it needed?

Wholl develop the procedures and limits?

How are test engines selected?

Once in place, how will the test be monitored?

Only after all the above have been successfully answered, usually over a period of two to three years, is a new test included in a new or revised engine oil specification.

Before getting to the meat of the subject, I want to cover a bit of history so the context is clear and you can see how this all started.

In the Beginning

Going back to the beginnings of engine testing, the need to demonstrate oil performance was driven by war. World War II saw the first test standards used to define engine oil for the military: U.S. Army Specification No. 2-104 for diesel oil, issued in 1941.

By the late 1940s, the American Petroleum Institute had developed the first engine oil categories, using ML, MM and MS to designate products providing essentially light, medium and severe operation protection. Shortly there-after, ASTM published document STP 315A, which described the engine tests needed to define these categories. The original so-called MS test sequences in STP 315A included test procedures from General Motors, Ford and Chrysler which covered wear, deposits, oxidation and corrosion as well as low-temperature control of sludge and insolubles.

Separately, the OEMs, especially heavy-duty engine builders, were issuing their own specifications and including their own test procedures, most notably the Caterpillar single-cylinder diesel engine tests which endure to this day.

Fast-forward to today, and we have a number of test protocols to define both gasoline-fueled (API S categories) and diesel-fueled (C categories) engine oils. The ILSAC GF series of specifications, controlled by North American and Japanese auto companies, is primarily for passenger cars and light-duty trucks and basically is the API spec plus fuel economy. In addition, we have proprietary OEM specs, such as those from General Motors, Cummins, Volvo/Mack and others.

So what drives the need for a new or upgraded test? Id say there are three factor to watch. First is an identifiable field problem that is not being captured by any existing test. One such example was the black sludge that plagued a number of passenger cars in the mid-2000s. After drivers complained and vehicle warranties were threatened, new performance tests were added.

Second, a new requirement may arise that current tests cannot define. For instance, using exhaust gas recirculation sharply increased the soot levels in heavy-duty engine oils; that too required more tests.

Third, there is the anticipation of new requirements that must be monitored. Case in point: engine oils contribution to fuel economy, that holy grail of test development.

Upside, Downside

Certainly there is plenty going on right now, with not one but two new categories under development. While the same basic parameters – lubrication, cleaning, sealing and cooling – apply to all engine oils, there are issues with fuel economy, emissions control and drain intervals that must also be addressed.

When you think about it, engine oils contribution to fuel economy is primarily a matter of viscosity and friction modification. SAE and the Japanese OEMs are attacking this issue through the development of a new viscosity grade, SAE 16. This will be the lowest SAE viscosity grade available, as measured by high-temperature/high-shear rate. Its viscosity will be 11 percent lower than SAE 20, the current low man on the totem pole in SAE J300. Friction will be reduced even further by using friction modifiers in the oils additive system.

The upside of these changes also brings a downside, and that is the impact they might have on engine performance and durability. Thats where engine testing comes into play. Lowering the viscosity is good for fuel economy, right down to where too much boundary lubrication occurs. Then you get into wear problems. Similarly, friction reducers are great – unless they are themselves corrosive, or have some bad interactions with other additive components or engine parts.

One of the toughest jobs is developing the procedures to measure the parameter(s) that are of interest. The people who do this are drawn from the OEMs, the oil industry and additive suppliers, as well as from two independent engine test laboratories, Southwest Research Institute and Intertek Automotive Research. Much of their work is done in task groups and in ASTM.

In addition, many of the best minds in the engine test business are involved with the various ASTM Surveillance Panels which oversee the standardized tests. They make sure the tests dont go off the tracks precision-wise and that parts and procedures are available. The Surveillance Panels have one of the most critical jobs in the industry, since product approvals would come to a screeching halt without the tests staying under control.

Engine Selection

And how does one go about selecting the proper engine for the test? A few criteria come to mind, such as: Does this engine have a problem with the parameters to be evaluated? Is it widely available? Will the engine be in production for a long time, and will the manufacturer agree to supply parts into the future? If the engine is critical to the parameter(s) being evaluated and is going to be around for a long time, it becomes a good choice to build a test around.

There are a number of practical considerations to weigh as well. Heres a simple one: How long will the test need to run to gain meaningful information? Engine tests can run for up to 600 hours, with diesel engine tests typically of longer duration than gasoline engine tests. Of course, the longer a test runs the more it costs.

Each test procedure is designed to mimic field operation and is based on field test results and customer concerns. That may mean the engine is run through a series of operational modes to mimic driving patterns; stop-and-go, hilly, on-highway, etc. Some engine tests run at steady-state conditions to stress the engine oil in a predictable manner. The information for the procedures often is supplied by the OEMs, who have access to more field data than any other source.

Test fuel is a critical piece of the puzzle. It needs to reflect what is currently in the market but also should have a large pool of background testing data. For years after leaded fuels were no longer in the consumer marketplace, they continued to be used in some engine tests. The argument for that was that other parts of the world used the tests and they were running leaded fuels. (No current tests use leaded fuels but correlations have been developed for them where needed.)

The average engine is built to production tolerances but that is not good enough for test engines. Engine blocks may need to be further honed to get to the tolerances required for statistical relevance. Sid Clark, Southwest Research Institutes OEM and industry liaison in Detroit, elaborated on this for me, using the Sequence IIIG oxidation and valve-train wear test as an example.

In this test, he explained, the engine block is pulled from the production line [before] the camshaft tunnel, lifter-bore machining and cylinder-bore sizing operations. Those operations are then performed at a precision machining facility to much more precise specification than normal production. The same is done with the cylinder heads regarding the machining of the combustion chambers, valve seat inserts, valve guides and valve spring seats.

All this is done because these are very special tests and we need to compare apples to apples in lubricant certification testing. Also, the Central Parts Distributor that supplies the consumable internal test components performs the same operations on many of the internal parts; i.e., pistons, rings, engine bearings and bushings, valve springs, valve seals, camshafts and hydraulic lifters, and even engine gaskets.

The Test Detectives

And once in place, how are tests monitored for ongoing performance? For that, lets look again to ASTM.

Once an engine and test procedure are proposed, the test is run with reference oils to determine first, if the test does correctly predict what it is supposed to, and second, if the test results are similar no matter what laboratory or engine stand is used.

Reference oils are maintained by ASTMs Test Monitoring Center, which assures that the composition of all reference oils remains the same from batch to batch, and that data from reference oil test runs are compiled to look for any drift or change in test results. From time to time, test results are adjusted to account for severity changes in reference oil test runs.

In the event something occurs which causes a major shift in severity, the appropriate ASTM Surveillance Panel may actually declare the engine test out of control. When that happens, people drop everything else to concentrate on what has gone wrong and how to bring the test back into compliance.

A good example of that was seen in 2011 with the Sequence VG test for oil sludging and deposit control, which is required for ILSAC GF-5 engine oils. The tests supply of reference fuel (which is also controlled by the Test Monitoring Center) had run out and a fresh batch was received. However, this new batch didnt perform comparably in reference oil test runs, so the VGs overall precision could not be assured – a major headache. That delayed the testing of a lot of new GF-5 formulations and there was a lot of pressure to fix things quickly. After evaluating the fuel and tweaking it, the reference runs came into alignment with expected results, and the test was back in business.

And the fun just keeps going! Right now, Surveillance Panels are looking at reference data, checking parts inventories, making sure that fuel is available, and handling all the other necessary details to maximize the precision of each engine test and its relevance to engine oil categories.

In the end, Ill add, sequence tests and bench tests only provide guidance for engine oil formulators. How the oil performs in your vehicle depends on a lot of other things that youve heard before. Just for the record here are a few reminders: Read your owners manual, change your engine oil regularly, drive smart (watch those sudden accelerations, etc.), and take good care of the other maintenance items like tires, brakes and so on.

If you do all that, the engine oil tests will have provided you with the best engine protection money can buy.

Related Topics

Market Topics