7th May 09 I have been running my PDI system now for approximately 4000 miles, don’t know where I have been it goes so quick. Anyway I am getting an average improvement of 13% over that distance. Not earth shattering stuff but an improvement never the less. To me that would mean a saving of approximately ?674 per year. So I do make the money back in year one. When keeping it for three years there is a big saving to be made. So that is the justification, I guess if you do 12k miles or more you break even in year one. But the power is just so great that is worth it on it’s own.