Engine break-in and first oil change interval... lots of opinions, but little data.
When I bought my 2004 Z4 I took it as an opportunity to get some limited data and, on another board, posted the following message which some might find of interest:
OK, there has been an ongoing debate regarding the need for break-in. Some posters have said that with the closer tolerances of today's engines, break-in is obsolete and one show "drive it like you stole it" out of the box. (as an aside, I never could figure that saying out. If I stole a car I would drive very carefully to avoid the attention of the police). Anyway...
I wanted to answer the break-in question, so I took an oil sample at 2,000 miles and at 4,623 miles without changing the oil. I then compared the wear metals in the oil at these two test points to see if there was a big difference in wear between the first 2K miles and the second 2.6K miles.
The results?
Well, to make things comparable I did two things:
1) I had a sample of the original oil with 14 miles on it analyzed as a baseline sample.
2) Using the total PPM (Parts per million) of wear metals I computed the delta between 14 --> 2,000 --> 4,623 and adjusted it to a PPM per 1,000 miles to show a wear rate.
The results?
Wear Metal, PPM/1000miles First 2K miles, PPM/1000miles Second 2.6K miles:
Iron, 6, 1.2
Copper 5, 1.5
Aluminum 4, 0.4
Conclusions?
Fact: As expected, there is a lot more wear taking place in the engine during the first 2,000 miles than subsequent miles. Wear rate of iron was 5 times greater, Copper 3 times greater, and aluminum ten times greater (these are approximate as the precision and accuracy of the original numbers is 1 ppm, yielding about a 0.5 ppm accuracy in my computed numbers). Chromium, nickle, silver and tin wear rate was below the level of accuracy making a comparision meaningless.
Implication: The concept of a break-in proceedure which "wears-in" the parts to each other is not obsolete. This is a strong implication, not a fact, as the oil analysis cannot really determine what an "improper" break-in would do, e.g., someone might say that while there is more wear during the initial miles, the value of a break-in proceedure has not been proven. And it hasn't. Only an engine teardown of two engines treated differently would ddress this directly. However, it is clear that the initial wear on the engine is significantly greater and it would only make sense to operate the new engine with this in mind, i.e., continue to follow a break-in proceedure which promotes safe wear-in of the engine parts to each other.
None of these metals are present in levels which would indicate the oil is "no good" or needs to be replaced. However, considering the relative cost of the vehicle vs. the cost of an oil change, this data suggests to me that an oil change sometime soon after 2,000 miles would not be inappropriate.
