I have a 2008 BMW 2-litre coupe diesel. At the time of purchase I also purchased the service package. The longlife oil has to be changed every two years or approximately 16,000 miles with my current driving style. I have changed the oil myself at 7000 in an effort to look after the turbo, as I am not entirely convinced that any oil can last 16,000 despite been assessed by the engine management unit for condition. The only problem is that by doing it myself I will lose out on BMW changing the oil and being able to take advantage of a very big service just before the free servicing runs out. The car sensors if I do a mid-term change myself will allow the car to go the full two years. Is it ok with this sophisticated oil to leave it in the car until the car tells me to change it or is this a marketing gimmick, and if left in will it put significant wear on the turbo?