If you are referring to terraclean, I had it done out of curiosity and only noticed a slight improvement in urgency but there is a big possibility that could be my mind playing tricks on me. And my mpg went back to what it was before I had it done too. I would save my money if I were you and buy something worthwhile. I would consider doing it again if I was to buy a diesel with high miles on it in the future but for a small petrol car that doesn't do many miles I wouldn't bother again.