And here we go again.....
Everyone knows better than the engineers that actually designed, built and tested the car.
Changing oil every 5000 miles is very much an american thing. I lived my entire life in Sweden up until 4 years ago, and european brands now either have a dynamic service interval with the first oil change made after about 15-18k (exception on M3 and alike that have a break in service at 1.2k), or they have a static interval around 18k (30000km).
Do you really think BMW or any european manufacturer would state 18k if it was harmful for your car? BMW has incentive in doing so as service is free, but Porsche (just bought a Cayman S), has the first service at 20k (no break in service). Porsche actually has incentive to make you change oil more often since it is not free, but still they call for 20k (or 12 months), why? Because the car will be just fine doing so.
If you sleep better at night changing oil every 5k, go right ahead, but you are throwing your money away in my opinion (and BMW engineers might agree).
2008 M3, Jerez Black, Premium Package, Technology Package, Moon Roof, Heated Seats, iPod adapter, SAT radio, Enhanced Premium Sound.