Just got a marketing email about this:
http://www.shell.co.uk/home/content/...uels/fuelsave/
Basically Shell are replacing their standard unleaded and diesel fuels with fuelsave versions now. They reckon it gives an extra 2% mileage which I'll take, thank you very much
The don't say much about the tech, but it sounds pretty much like they just add similar cleaning additives to it as they do with their V-Power diesel range (or I do with my redex )