So thus far, nobody has reported carbon build-up issues.
Model year - 2011
335d or X5d -335d
Mpg - 26.7mpg
Avg speed 33mph?? (will double check)
Brand of fuel - usually BP, unknown cetane
On a scale of 1 to 5 how hard do you drive? 3
Highway/City Mix - 40/60
Carbon build up issue yes or no? -None that I know of
EGR warranty was done, but no other work has been needed. Definitely more reliable (knock wood) compared to my 135i with its fuel pump from hell.
2011 335d / Deep Sea Blue / Saddle brown / sport / premium
2008 BMW 135i / 6MT
2002 Z06 Corvette