Originally Posted by powers1

Diesel oils are not dirtier than petrol versions!!!!In the case of the X5,
Bmw recommend the same oil(Longlife),the same spec(ACEA/A3/B3/B4) and the same viscosity (15W 40).Infact,for the Diesel they prefer to use the ACEA/B4 which has a thinner viscosity(5w 40).Dont take my word for it!As I said before in my earlier post, all this info is on the owner´s manual.You can use Mobil1 or any make of oil,providing it conforms to BMW´s specs,you should not have a problem.Here in Europe,BMW recommend Castrol 10w/60
but I find this oil to have a bad odour and the engine is not as smooth as with
Valvoline or Mobil1.