Hi, I use only premium diesel in my audi a6 c6 Le Mans 2.0 tdi. It is a 2010 model with 129k. Would anyone advise on adding additional additives e.g. Millers, max tane. I am just giving the names of some that appear as good brands with good reviews. Majority of my driving is city driving with traffic, I usually average 8mph with an average of 18-25mpg. It states that I should be getting 39mpg. I do usually cold start drive but there must be a way to improve mpg. I look forward to your replies.