Market Topics

Automotive

Share

For us old hands in the automotive lubricants business, engine testing is an integral – dare I say crucial? – part of the process of bringing a new engine oil to market. After the preliminaries (selections of base oil and additives, as well as bench testing), we queue up the engines.

Of course, there are some proprietary bench tests that additive suppliers and oil companies run to make sure they have selected the right mix of components. It would be great if these tests also could demonstrate performance in an actual engine, but there is a problem. Every one of these screening tests seems to have some bias built into it. This bias may be the result of the additive system used, test conditions such as temperature, catalysts, or a number of other variables.

And lets face it: In the real world were trying to lubricate an engine, not glassware or a metal strip. Even if the metal strip is an actual part from an engine (like a piston liner or bearing material) its rare that actual operations can be correlated to the bench. To approximate the real world, we still fire up costly, time-consuming engine sequence tests.

To date, the ball rust test is the only laboratory bench test to have won a place in the standard test repertoire as a replacement for an engine test. Previously, the industrys standard engine test for rust resistance by an engine oil was the Sequence IID – and the BRT was correlated seven different ways to Sunday against the IID before gaining acceptance.

The first laboratory tests of engine oils go all the way back to the early 20th century. In the 1923 edition of SAE J300, the venerable engine oil viscosity classification standard, requirements in addition to viscosity included flash point, fire point, color, pour point, carbon residue and corrosion resistance. While these tests didnt assure improved performance in an engine, they did set a standard for the types of base stocks used. (Remember, engine oils in the 20s didnt contain any additives.)

Historically, the first additive-treated engine oils (designated heavy-duty) were introduced into the commercial market in the United States in 1939. Actual engine testing of oils started with World War II, when U.S. Army Specification No. 2-104 was issued in 1941. It included basic deposit tests as well as corrosion tests. From then on, engine sequence tests have been the vital link between formulated engine oils and actual applications.

For a large part of this time, engine test procedures had enough local options as to operating variables that it was possible to get passing results with marginal oils. As an example, by controlling the inlet air humidity (which was not specified in the test procedure at the time), it was possible to improve a candidate oils performance in single-cylinder diesel engine tests. There also were so-called easy engine test stands which seemed to perform well no matter what, and often without a clear reason as to why.

In time, automotive manufacturers began to suspect that questionable oils were being approved for use, and wanted a better process for evaluation; hence the Code. In an effort to level the playing field so all oils would be required to meet the same standards, the Chemical Manufacturers Association (now the American Chemistry Council) developed a process in 1992 called the Petroleum Additives Product Approval Code of Practice for engine oil testing and approval. The Code, which celebrates its 20th anniversary at the end of next month, was a response to concerns raised by the OEMs regarding engine test validity.

The stated purpose of the Code is as follows: Implementation of this Code in engine testing will provide more accurate performance results, thereby yielding more cost-effective engine testing – a mutual benefit both to lubricant formulators and their customers. In addition, communications between sponsors and customers will be improved because standard practices are described in detail. Of course the devil is in the details.

There are 11 appendices in the Code covering all aspects of the engine and bench testing process. One of the appendices (K) describes in detail how a new engine test is accepted for use in evaluating engine oils.

To study the Code in depth, you can find it at http://www.american chemistry.com/Products Technology/PAPTG/PAPTG-Code-of-Practice-Resources/default.aspx.

Not every engine test is covered by the Code; some proprietary tests are controlled by individual equipment manufacturers. But every engine test that supports the current API and ILSAC engine oil categories is in the Code.

Before an engine sequence test is accepted into the ACC Code, how does it first see the light of day? Who starts the process, and what happens before the Code is applied? Lets step back for a minute and realize that no engine test starts out without a property to identify or a problem to solve.

For example, when fuel economy first became an issue in the 1970s, the question arose, how do we evaluate the effects of engine oil on fuel consumption? The first effort was based on a chassis dynamometer procedure using federal emissions test protocols. This was referred to as the five-car procedure because it used five different vehicles and measured the fuel economy benefits as an average of all five vehicles. It was expensive, and notoriously insensitive to engine oil formulations.

In the meantime, other procedures were tried using engine test stands and various engine configurations. One notable method used an engine which was not fired and in fact had the spark plugs removed. The procedure basically was to crank the engine up to a certain speed and then let it coast to a stop. The longer it coasted, the lower the internal friction in the engine. By comparing the test oil to a standard reference oil (run on the five-car test), it was possible to estimate the fuel economy gain.

Finally, a new engine test – the Sequence VI – was proposed to measure the engine oils contribution to fuel economy. It would use a fired engine run through a specified operating cycle and compare the test oil to a standard reference oil. The engine was offered by General Motors and a procedure was developed in ASTM by representatives of the additive industry, the oil industry and the OEMs.

Since its debut with the ILSAC GF-1 oils of 1992, the Sequence VI test has been modified to bring more discrimination and to try to identify the effects of not only viscosity but also friction modifiers and general additive componentry. Its current iteration is the Sequence VID, or six-D.

The history of other engine tests follows a similar path in that a need is identified in the field; a proposed test procedure and test engine are identified; and representatives from the various segments of the industry work on developing a methodology to evaluate the engine oils performance against the targeted need. Reference oils representing failing and passing performance in a test are selected, and then formulated and distributed by the Test Monitoring Center (TMC) to provide a common standard to everyone who runs the test. In addition, TMC monitors test repeatability and reproducibility among the various organizations running the tests.

It gets even better, as there are regular meetings within the test laboratories to make sure that some of the subjective aspects of engine testing are uniform. When an engine is torn down after a test run and the parts are rated as to how much sludge or varnish has developed, it comes down to how a particular person sees the deposits. The raters are all tested regularly to make sure they are all seeing and scoring the deposits the same way.

During the course of developing a test, a lot of negotiations occur. Sometimes there are disagreements about test procedures and limits. These are negotiated within the ASTM system and usually represent some compromise position. The industrys ability to come to a consensus is a real testimony to the integrity and commitment of every one of the people involved.

So to recap: A need is defined, a potential procedure is developed, hardware is identified, test matrices are run to measure performance of passing and failing oils and to set limits. Industry organizations are assigned responsibility for managing the tests operation and reference oils, and finally a new category specification that includes the test is issued. None of this happens in a vacuum since we all talk to each other on a one-on-one basis, within our own industry such as in APIs Lubricants Group, or in an inter-industry forum such as ASTM or the ILSAC/Oil Committee.

I would speculate that some of you readers think that these procedures occur in the dead of night while there is a full moon. I can assure you that nothing could be further from the truth. There is far too much at stake to allow a new test to become a part of industry criteria without the input of everyone who wants to participate.

If you are concerned that your point of view is not being addressed, I encourage you to become involved with any of the organizations which play a part in our business. ASTM is a great place to start and new ideas are always welcomed.

Related Topics

Market Topics