C12?!? WEAK SAUCE!!! You better turn that puppy up if you want to get anywhere and not kill yourself on fuel. We've got a truck at work with a C13 that's in a mulch blower tri axle and that thing doesn't have the balls to get out of it's own way. I don't think it even has a Jake on it.
It's a mlb or mbl? I get a steady 5mpg. It sucks but it's very reliable to me. Me Haney over on the truckers report is going to reflash my ecm if my dot goes good in two weeks. It's a slow Turd But it works