The above posts are spot on and consistent with our recent 5,000+ mi. trip through the Rockies to KS, then down to NOLA and back to SoCal. To average >30MPG with the '10 35d you'll need minimal elevation fluctuations, with <70MPH speeds. FWIW, I can "old man" the X5d around town to acheive ~25MPG - but at the expense/risk of P.O.ing almost every other driver in the city.