I have just started using Millers Diesel Sport 4. My 2.0 TDCI 75K was hesitating quite a lot around 2k revs and eventually became undriveable as the hesitations turned into loss of power which was only cured by turning the engine off and back on again (not good on the motorway). Anyway, I serviced the car (oil / oil filter / fuel filter / air filter) which helped a lot but the hesitations at 2k revs still persisted. I suspected the injectors may be clogged so I have double dosed with Millers and am currently on the2nd tank at this dose.My car is currently a joy to drive, plenty of power and only a very slight hesitation when the engine is cold and uphill. Am not sure whether this is due to the raised Cetane levels that are in the current double dose of millers or the fuel system has cleared out. Iam planning to do a couple of tanks at normal dose and then back to no additive to see how the car reacts. My carcertainly has more power at thedouble dose and is a lot smoother between the 1.8 - 2.2k rev range thatFord diesels seem to sufer from. Icant tell whether im getting more mpg yet andhave carried on using ASDA fuel through thisexperimentation. I think if your engine is already running well you probably wont notice much difference but if your fuel system needs a clearout the detergents in Millers will help.
I tried Millers Power Diesel Sport 4. Didn't notice any difference... may be more useful/noticeable if you do the kind of driving that causes the injectors or exhaust-side to get clagged up. Mine spends much of its life on the motorway.