been putting the recommended 50ml per tank full in the Leon (CR TDI FR) since the day i got it, well the first tank full i put in it...
i cant honestly say whether it aids mpg or not, the average mpg since i got the car is 47mpg, this hasnt been reset since day dot either and there is now just over 12K miles on the clock (got the car in Jan this year).
the other week i was putting the additive into the tank when this guy walked over and asked me if the car had a computer on it... i looked at him with a puzzled face and said yes, an ECU... he then proceeded to tell me that i shouldnt use the additive, i told him it had been fine for the last 6 months on it to which he said Peugeot told him not to use it... i just raised an eye brow and he walked off in the end...
my bro has a Golf mk5 tdi (PD 170) and when VW serviced that last they said there was some contamination in the fuel. they checked the fuel system and couldnt find anything wrong though, he also uses Millers additive...
to be honest, i think if i stopped using it now i would convinced myself that the car was slower, less responsive or that the mpg was suffering...
your damned if you do and damned if you dont !