I thought that your readers may find this interesting: I currently run a Peugeot 206 1.4 HDI turbodiesel. My motoring mainly consists of a 36-mile round-trip commuting into Dumfries each day. Until recently I was filling up with supermarket diesel near to my place of work, and the car had averaged 65mpg over the last couple of years. Two months ago I needed fuel urgently, and filled up at my local Esso garage. Since then my 206 has averaged 74-76mpg, and power delivery seems smoother and more responsive. I do not think that I shall be using supermarket diesel again.