Hi all, first posting so please be kind to me.

Got an 2.0 Tdi Sline A6 registered in 2005 and noticed of late that the MPG's has dropped drastically from around 67Mpgs to late 50's on decent run.

Been told that I can add an additive via the fuel tank that would improve the MPGS but not too sure if this is correct .

Car does 65 miles a day mostly all motorway driving.

Does the filter need to be replaced or can I add this additive and burn off the excess soot?

Help & advice would be greatly appreciated.

Peter