I just bought my first BMW, finally. Its a 6 year-old X5M with 99k kilometers. Looks and runs great. This is supposed to be an all in one vehicle replacing for now the idea of VW Atlas and an M3 convertible Having lots of fun given low end torque) As expected also had to buy a litre of oil... within the first 1k! Dealer said he had full synthetic 5-40 in there so thats what I poured in. Is it the best oil? As you know manual allows a choice of many...