Service interval is 15k, way too long for my taste. Because of the Synthetic Oil, most BMW mechanics around here recommend 7500k, anything less is a waste of money. I planned on doing mine at 5k & 10k, and let the dealership do there scheduled 15k. And since the oil fuller cap says "Castrol" on it. I found Castrol Full Synthetic at ( now dont laugh, Guy's ) Wally World (aka Wal-Mart) it's only priced at $18.88 for a 5qt container or (Imperial gallon). That's $3.77 a quart, can't beat that price. :thumbup: