Same year, model 2500 170" wb and aprox 50/50 city/hwy and have only gotten less than 19 once after 14,000+ miles. Estimate average 20.5 mpg. Do you use a ScangageII or similar device? If not search postings by forum user sailquik to get your mileage up. Trips almost to weight capacity still get low 19's.2013 high roof, extended body....5,000 miles 16mpg. 60%city 40%highway. im not complaining as my old f250 got 7mpg (liftd on 35's).