Quote:
Originally Posted by Bror Jace
Trebuchet03, the resistance to a heavier fluid is hydrodynamic drag. Since the engine parts push the oil out of the way as it turns, the heavier (greater resistance to flow) the oil, the greater resistance for the engine ... otherwise known as higher load.
Coefficient of friction is different. They must use fluids of equal weight (cSt - centistrokes) and then rub one surface against another (say, a small polished metal plate against a larger flat surface) and then measure the resistance.
That's just a guess ... but some SAE-type tests are actually that simple. Ever see a Timken bearing machine used in oil tests?
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That's all well and good - but I stand by my original statement
Quote:
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...friction goes up as contaminates accumulate and additive packages deplete... But to say my long oil change interval = accumulated bits and depleted additive packages is a fallacy.
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As for the timken OK load test machine - yes, there's one (well, probably more than one that I'm unaware of) @ my school's shop. But, it's a qualitative-relative test. I'd get slapped (and/or, a good talking to
) if I reported the results at face value rather than comparing one sample to another one. There are much better quantitative-discrete tests which are used
