I like to clarify the break in period.
A motor needs to be broken in when the motor comes from the factory with "break in" oil. This is a low quality oil that speeds up the break in process (wear), because it has very little additives (piston rings and cylinder walls especially). That is also the reason for keeping the rpm low. This was still the case for the M3 E46. The N54 comes allready with synthetic from the factory, so isn't it obvious that there is no break in period (maybe they do it at the factory, don't know just guessing)? This is only possible due to the minimal tolerances and todays superb manufacturing processes.
FYI, the N54 block is made of aluminum alloy with cast cylinder liners.
Just my 2c's
