I hope this post saves some poor guy from thinking he can get the mileage #'s some of you guys are posting.I am on my second duramax after lemon lawing my first one.Total mileage over 100k and neither truck ever saw over 17mpg,that includes empty, downhill,tailwind,drafting,etc.This is a reg. cab 4wd 9,200 gvw truck that usually runs 65-75 with cruise control @ sea level.P.s.I've been a professional mechanic over 30 years and this truck has been on the dyno and had parameters checked with a tech 2 @.worst mileage was 9mpg towing 10K lb boat