I am curious as to how the engine seized? Was it a small leak at first and developed into a large one? Did you run it with little oil while on the highway to cause it to seize? Reason why I asked is my old X5 4.8i had a small leak for a week and all the sudden started leaking a massive amount while driving on the highway (you could see oil leaking when looking under the car). I was so fed up I just traded it in with the leak and accepted the small amount the dealer offered so I unfortunately do not have any answers as to what broke.