All _______ are Created Equal?

   Mercury Marine has made a point of advertising that not all TC-W3 oils are the same, and they've run a test they say proves it. They took two 15-hp Mercury outboards and put their own brand of TC-W3 in the fuel for one, and another OEM's oil in the other. Then they ran the engines for 100 hours.

   They took pictures of the results. Neither oil left much of a carbon deposit, but there was noticeable scuffing on the piston of the engine run on non-Mercury oil. Pictures of these results have been printed in their catalogs and dealer-information packets.

   Was the test fair? Ray Donahue, Director of Advanced Materials for Mercury, and chairman of the NMMA oil-certification committee says the fuel, engine condition, and other test procedures were identical, and that the tests were run by an independent lab. And the competitor's oil is a currently marketed TC-W3, although Mr. Donahue said, "it had the highest scuff allowed to be still passable.

    But, and here's the kicker. Instead of mixing the oil in a ratio of 50:1 as called for, they mixed them at 100:1 for the Mercury tests. Is running an engine this lean "real world"? Donahue told us some boaters push their engines wide open and create the same situation. An engine can run extremely lean if it's opened up too rapidly, but once running at full throttle, the proper mix is restored.

   What does this tell us? first, consumers can create conditions to show the weakness in their motors and motor oils; and second, that outboard motor oil can have different characteristics. Both oils passed the standard, and both oils should prevent scuffing, to a similar degree, when used in the proper ratio and with good fuel. But let's face it, boats aren't used like cars and the fuel in those tanks can sit for weeks or months.

  The basis for this test and article was run about 6 years ago, but I doubt things have changed much. Informing the consumer that the way he maintains and uses his boat can effect the choice he should be making when purchasing fuel and oil is an important one.

One last thing to remember is that the fuels on the market today are designed to be stored in pressurized fuel tanks with evaporation recovery features. Boats do not have this feature and over time, octane boosting additives put into gasoline evaporate, leaving a lower octane rating for the fuel. Here's where quality oils added, can play a bigger part in the engine protection formula.

See this section for information on oil classification concepts.

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