I care about consumption because I have been lucky in the past to run a m sport 335d for 2 years, all the real world performance in the world and I regularly got 900 km out of a tank...then went to an m3 which I loved, but had 2 years of very regular visits to the petrol station...now to the f10 m5 I've only filled it once so far but it's looking like its exactly the same as the m3....But feels like the 335d in terms of surge, and is much bigger which suits the school run etc...
One day I will do the rational thing and buy a 535d m sport...especially as one of my bus partners has a panamera diesel! (lucky the other has a TT S6 Audi...)
The diesel was great never having to fill it up! Plus I like to know the numbers!