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      01-11-2013, 05:50 PM   #18
piloto
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Drives: 2011 E90 M3 - AW/FR
Join Date: Jun 2010
Location: Orange County, CA

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Oil consumption is not related to break in. Abuse? Yes.

You'll abuse your piston rings and wear them out faster if you're revving the engine to high rpm without properly warming it up and allowing the oil to reach its optimal temperature. The higher you rev, the more friction, thus more wear you'll have in the piston ring. Engine oil, when at optimal temperature combats this and helps reduce the wear.

Build (manufacturing and assembly) tolerance, especially around the valve guides and piston rings, average operating temp of the engine as a percentage of the time it's on, PCV valve condition, main bearing seals, straightness of the cylinder, etc. all have much more to do with oil consumption than anything else. Engines have A TON of moving and mating parts, and anything that's mass produced is going to have some amount of tolerance. As special as the S65 is, it's still a mass produced engine (so are the AMG "assembled by hand" engines for those keeping score at home).

To make parts with zero tolerance is just short of impossible for anything that's mass produced. You'd reject most of the parts made and it would cost a fortunate and take too long. So there's manufacturing tolerance on each component, and then that tolerance compounds (known as tolerance buildup) when you mate all of these parts together. So it's enviable that some will have looser gaps and others will have tighter gaps.

Heck, even the alloys will vary slightly in their buildup. For instance, specs would state that 7075 Al is made up of 5-6% Zinc, and 2-3% of Magnesium, amongst other raw materials. Well, the coefficient of thermal expansion for 7075 might be assumed to be fixed, but it'll vary every so slightly based on the tolerance of the various raw materials that go into it. Is this enough to make a noticeable difference in an engine? Likely not, but it just point to the fact that it's another variable that can contribute to it. So take all of those variables, add them up, and you'll have some noticeable difference.

The fact is that all cars will consume oil. It's just that 1.) you don't have a very accurate way to measure the amount of oil that's actually in your engine at a given time, and 2.) if your driving style and other variables listed above contribute to a slowe consumption rate, you'll never notice it because by the time it would be noticeable, you'd have changed the oil already.

The old days of having tons of larger (relatively speaking) metal shavings in the engine that would score the rings and cylinder liners no longer exist. Yes, there are still microscopic bit and pieces and always will be, including regular dirt that gets past the air filter and deposits that are in the fuel. This is why we change the oil filter regularly.

In any case, you're engine is already run hard once or twice, before it ever gets into the car as part of any testing process.

I'm not debating whether you should follow the manufacturer's recommendation for break in, but I wouldn't conclude at all that it relates to oil consumption. Read up on the motoman method if you're really interested to learn more about different thought processes behind engine break in, at least about the theories behind them.
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