My friend has what he calls "his baby" a BMW 325Ci. He rarely drives this thing and it shows with only 3,000 km's on it. He takes it out about twice a month on the highway to strech its legs and thats about it. He bought this car brand new and has had this car for little over 2 years. I was shocked when he told me that he still hasn't changed the oil. I checked the oil for him and the color seemed "normal" but it was a liter low (car takes 6.5 liters). I also noticed the oil fill cap reads "Castrol Only" on it. So what do you say, Castrol Syntech 0w-30 "German" or the Syntech 5w-40 "Belgium" for this -rarely- driven BMW? Thank you.