I know this is the # 1 question asked. What is the mpg on an excursion, well I am looking into buying this used 05 excursion. It has the 6.0 diesel engine, 4x4 limited version. What can I expect out of this monster ? I heard that with this ultra low sulfur fuel that an additive needs to be added every time one fills up. The additive is to help lubercate the fuel pump or the injectors, something to that mater. Any info you give me would help.