IMO if your planning to keep a vehicle for the longer term then regular servicing is important if you want in this case your BM to reward you. I change my oil and filter every 10ks as I plan to keep my 05 diesel for a long time yet, if my turn around was four years I wouldn't be so diligent. With the oil filters I purchase MANN brand who make filters for BMW, I pay $48 for an oil filter and $58 for an air filter way under BMs price. www.hvfs.com.au As for your oil I don't know wether your X is petrol or diesel.