Mike is correct. Engines today have much better/higher tolerances than in days past. Most manufacturers put every motor through a break-in test, sometimes simulating 500 miles of all rpm ranges. Better to break something now in QA than pay for it later. I toured both the BMW and MB plants in Germany one Summer and the type of testing they do there makes you wonder if you need any engine break in...even though the brake pads/rotors do need it. I remember specifically the BMW I-6 motors (back in '96) were run "extremely" hard before installation!

Tom

 

Reading over in the BMW Raodfly forums, it was noticed once that the break-in driving for the E46 M3 should be short trips 10-20 minutes that include varying RPMs. This allow the connecting rods to stretch when under high RPM/Load. In theory this would result in the longevity of your compression ratio. However highway driving (or constant rpm, little load) will allow for all you moving parts, especially the linear ones to seat themselves nicely. This is what I understand.

Mike.



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