Yours sounds pretty typical. On average I`m getting about 10-11 mpg on my 06 2500 4x4 5.7l. I have seen as high as 14 mpg on highway. While towing a camper about 8-9 mpg. I will be changing my muffler soon with a performance one. Mostly because the old one rusted out. BTW, I don`t see him as complaining. Just asking a question.