As good as the owner maintained them
I've had 2 now, manuals. They delivered 5.5L/100km combined cycle. I'd guess the Auto should be between 6 and 6.5L.
Clean the EGR, service the auto and it should last quite long.
If you want it to really do well, clean the intercooler, replace vacuum lines, bypass EGR and clean it, Oil Service it every 7500km and block off the vacuum manifold except the turbo line.