just wondering if anyone has tried this,

http://www.halfords.com/webapp/wcs/s...Id_165750#dtab

i know the topic of fuel additives is keenly debated with those who believe they do nothing and those who feel they are beneficaial.
i normally use millers 4 sport and notice that mine gets better MPG, smokes less, revs more freely, less diesel knock and is generally smoother.
so was wondering if anyone had tried this and seen any benefits from it, does it do what it says on the tin so to speak.

TIA

colin