My 2005 Vectra 400 Cummins get only 6.7MPG. No matter what speed (within reason), weight, towing or not my milage stays at 6.7MPG. I think that is way too low. I took it to Freightliner and the RV dealer and they say this is normal but as I meet other RV owner with about the same size RV and same type/size engine they tell me they get 8+ MPG. Others have told me it will get better after break in - but I have 18,000 miles and it isn't getting better. Even one MPG better is a significant savings - any help?
