Hi
I am under the impression that when the VE introduced the "SIDI" version of the V6 engine they drastically reduced the timing chain issues but I am sure some others will chime in with further input.
I believe in a mountain type area your fuel consumption will be just over the 12 litres per 100km range. I currently use a VF SV6 ute for daily duties and it averages 11.3 litres per 100km in the city area.
Regards,
GTSRVF