Everybody makes claims of their 3/4-1t diesels pulling 20+ MPG's but in reality it only happens when it's totally unloaded running 65-70mph down a smooth interstate without the sight of a hill. All my years of working on them have shown real world results closer to 15-17mpg's which IMO still isn't bad. Biggest problem comes to new regen trucks that are bought only as a daily driver. That's pretty much why I went with the Hemi, all conditions being perfect I've seen 22mpg's in my quad cab.