I usually put a bottle of this in every month, each of my MOT emissions the car is spot on ( 12 year old beema) just normal mileage & the stuff will do its work, there are a lot of things as said that can effect your fuel but that's been said in previous posts, how did they find the fuel consumption? have you checked for leaks? With respect, you do not get much now for £20. Do not take your car to the likes of K.F.+ Hal fords or the dealer, they will rip you off, look for your local family run garage.