The book says change every 12,500 miles. I had a 405 a few years ago and it was 2,500 mile then a golf at 5,000 miles then a A6 at 10,000 miles. I know it is fully synthetic oil but would it be better to drop it back to every 10,000 miles or lower ?. My car is a 2008 model with 75,000 miles. I have being using Castrol edge oil at the servicing and the little Honda one ltr cans for topping up between oil changes.