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Recently I got a note from a reader regarding my column on the California government website that offers advice to consumers on their oil drain intervals (March 2012). His concern was not so much with the website as with the fact that I didnt extol the virtues of synthetic engine oils for longer drains. My purpose was to question government inserting itself into a matter of personal choice, so the column didnt go into any discussion about long-drain engine oils.

However, the reader did get me thinking about long-drain oils, and how we can convince ourselves and others that some oil formulations are suitable for use well beyond the change intervals recommended by the automakers. That led me to ponder how we perceive claims made for drain intervals, and how to appraise them. From there, it was only a small jump to Einstein.

Albert Einstein was probably the most brilliant scientific mind of this age, or perhaps any age. He was responsible for completely turning physics on its head and he did it with thought experiments. That is, he conceived of possible ways to test his hypotheses and let others do the actual tests.

Whatever worked for Albert ought to work for me too (as long as it isnt quantum physics). So I want to propose the following thought experiment:

Lets assume there are identical twins living in Seattle. Let us also assume that they drive identical vehicles – make and model, year, engine -transmission combination, etc. Now let us assume that Twin As vehicle is a taxicab, and Twin Bs is a messenger vehicle that makes a daily round-trip drive, from Seattle to Vancouver, Wash., and back. Thats a round trip of about 330 miles taking about five hours. Further, both twins learned how to drive from an excellent instructor, and they both drive in exactly the same safe manner.

If the twins vehicles are maintained by the same garage, the same oil is used, and the oil drain interval is 6,000 miles, which vehicle would be expected to last longer, and which vehicles engine oil would look better when drained?

This is a question that original equipment manufacturers have asked over and over. They have run field test after field test to verify the durability of their vehicles, and continue to do so today. They are always glad to hear satisfied customers tout the quality of their products.

The same can be said of many oil marketers and additive suppliers, who also run field tests to determine how well their products perform and protect their mutual customers vehicles.

Performance categories maintained by the auto industrys ILSAC group and the American Petroleum Institutes Lubricants Group provide guidance to engine oil purchasers as to the expected performance of their oil, as measured by a series of bench and engine tests. These tests are designed to emulate field test data which have been generated by the OEMs, oil marketers and additive suppliers.

OEM-sponsored field tests usually are designed to either solve a potential deficiency observed in the marketplace – like the widespread sludging problem seen a few years ago – or to secure a desirable improvement in vehicle performance. The original engine tests from the 1960s were devised to predict engine oil characteristics which were identified with performance issues in the field. Since then, field testing has been the main reference source for new and updated engine tests.

For those who arent aware of what each test is designed to cover, the table below shows a partial list of the tests for ILSAC GF-5 passenger car engine oils, and what they predict. When you purchase an oil, the API donut and ILSAC starburst symbols give you assurance that it has been tested in accordance with industry standards and is suitable for use in your vehicle.

This testing is designed to assure performance when engine oil is used at the vehicle manufacturers recommended drain interval. When you extend the drain interval beyond recommended levels, you are in uncharted territory. So what should your criteria be, if you do decide to extend your drain interval?

For many oil marketers, there is nothing more valuable than a satisfied customer. The testimonial is a staple of the oil industry (and many other industries as well). But does anecdotal evidence really mean anything, other than someone likes the oil?

Lets go back to the thought experiment: Twin A would be likely to say the oil worked okay, but nothing special since taxicab service is severe. His engine oil likely would look pretty dirty after the very first oil change, and there might even be some visible wear on the engine. Analysis of his used oil samples would probably show a pretty stressed-out oil with a lot of sludge and fuel dilution.

Twin B on the other hand might actually rave about his experience since he is doing mainly highway driving and in a temperate climate. After 100,000 miles, his engine would be cleaner than his brothers with less visible wear. His oil samples would look a lot less distressed because of the type of driving hes doing.

We could add a few parameters to our thought experiment to increase the reliability of the results. For instance, we could add more vehicles, since a typical field test has a lot of variables that cant be predicted, such as accidents or vehicles being stolen. We might have to find more twins trained by the same instructor who also own taxicab and messenger vehicle pairs, although driving technique is less important if we have multiple vehicles; that tends to minimize driver differences. Wed also have to premeasure and rate critical parts in the engines such as cam lobes and lifters, cylinders and pistons (both skirts and rings), and main and rod bearings, to name a few. That will allow us to remeasure at the end of the test to see what happened and how well the oil actually protected the engine.

Lets also add a lot of specific oil analyses, taken at precisely staggered mileage intervals, to determine just what is happening to the oil itself. We could start with a look at the new oils properties, to see how it changes over time, and stockpile enough oil so that there wouldnt be any batch-to-batch variations. In addition to various viscosity tests, wed need to measure oxidation by infrared or some other analytical technique, fuel dilution, used oil insolubles, metals (both additive and wear) and other properties.

In the end, wed have enough data to reliably make claims for the performance of the oil; that is, a field test. There wouldnt be a lot of uncertainty about the operating conditions, which would remove that variable from the evaluation. We could then add testimonials from drivers, fleet owners and maintenance managers.

The bottom line to all of this is that we need field testing to verify product performance. There are no ifs, ands, or buts about it. Field testing is the real world. Sure, its controlled but it involves actual vehicles in actual use, not an engine test stand or even a computer simulation. It is the clearest demonstration of an oils actual performance, not a projection.

There is a place for individual customer testimonials, or even great piles of them. We are very prone to accept endorsements from friends, relatives or celebrities of any products performance. They usually represent some degree of satisfaction with a product – but they dont reflect a technically sound analysis of the oils performance.

Ill leave this with another thought, not an experiment. Every time you change your oil, look for data that supports the product claims. Maybe it will be the API donut or ILSAC starburst on the container, telling you that your oil is tested and licensed against the latest requirements. You might even look for some literature from the oil marketer showing field test results.

If you do, Albert and I will have had a successful thought experiment.

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