The 6.8 in 05 was a good moter it when from a 2 valve to 3 valves a cylinder. The spark plugs blowing out was solved as well by 05. If your not towing you will get between 14.5 and 16 mpg on hiway and between 9 and 11 mpg overall around town. All depends how fast and into the gas you drive. I have a gas and a diesel and with diesel almost a dollar a gallon more I find that it is a wash in fule cost. Cost the same in gas or diesel. If you tow you will drop about 35% in fule millage hope this helps mal11963
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