Very simple. Before I took delivery of the Volvo S60 D4 181 I ran for 6 months and 7,000 miles, averaging 61mpg, I had a discussion with Volvo's engine man and he gave me a piece of vital information that I have been trying to get across to the public for the past 18 months: All new engines are optimised for the ECDC tests on the very best fuels in order to get the very best results, and that means Shell V-Power Nitro Plus Petrol or Diesel. If you run this engine's very sophisticated injection system on anything else you are looking for the sort of trouble you experienced. Beats me why the dealer didn't come clean and tell you this in the first place.