Oil Changing Methods

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Nov 18, 2003
I've read an article that stated that the engine wear rate actually decreases, up to a certain point, as the engine oil is used for some time. This may sound crazy, but could there be some advantage to draining/replacing 1/3 of the capacity of the engine at 1/3 the mileage interval? For instance, if the capcity is six quarts and the oil is normally changed at 7500 miles, you would drain and replace two quarts every 2500 miles.
I think your gains would be marginal at best. There have been several UOA's around that show low engine wear on a regular 7,500 mile interval. You may be getting less wear, but it may not really make a difference in the life of the engine.
I don't get the point. Assuming the wear rate decreases with time, would't you want to leave it in there the whole time? Why drain out that "good" used oil and put in fresh stuff?

I don't know if I agree with the idea in the first place, but even if it was true there would still be no point in diluting the "better" used oil.

I think the article is blowing smoke. If this were true, don't you think the motor oil producers would tap into the huge supply of cheap used oil and formulate their new oil that way?
Supposedly, the wear rate was lowest from 3000 - 5000 miles on the oil. Above 5000 miles the wear rate increased. Presumabily, there was some friction reducing benefit from oil with some mileage, although I don't recall any results on horsepower or fuel mileage. I thought that changing the oil in three increments would still allow a complete replacement of the oil as a normal drain/replace cycle to keep the TBN up, while still maintaining some aged oil. Just a thought.
This rumor was started by this study: http://neptune.spacebears.com/cars/stories/oil-life.html.
It's just some guy doing oil analysis like we all do. Anyways, the Mobil 1 showed higher wear in the first few thousand miles than in the later miles, so they jumped to the conclusion that new oil must not protect as well. What they overlooked was the fact that the higher wear was occuring during the car's natural breakin phase. So no, changing oil early is not bad, this is just a rumor started by people misinterpreting their test results.

[ May 14, 2004, 05:40 PM: Message edited by: Palut ]
I wonder if this lower wear occurs when the oil has sheared down to a 20 weight and is behaving like 5w20?
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