The second-generation BMW 6 Series is almost everything a grand tourer should be. To many eyes it's not good looking enough, with its moustache-like grille and awkward rear-end. But otherwise this is a true GT car, with effortless performance, mile-munching comfort, and crisp handling. As a used car it's now relatively affordable, and the availability of a diesel engine means you won't have to smash a piggy bank to cover running costs.