Costs & verdict
Everyday costs, plus how reliable and safe it is
In terms of purchase price, the S6 fits between the BMW 540i and the Mercedes-AMG E 53, while resale values for all three should be similarly strong. It's worth bearing in mind, though, that the regular A6 50 TDI does almost as much for a lot less money.
When it comes to fuel economy, Audi’s decision to go with diesel power gives its car an advantage over its petrol rivals: the S6 tops 35mpg in official tests, whereas its rivals return nearer 30mpg. What’s more, the difference is only likely to grow in the real world when you start putting your foot down.