I have the V6 so probably no help. However, I think the V6 is sensitive to fuel. My mileage drops off every winter and then spring comes and it goes back up. It is usually about a 1.5MPG sometimes 2 drop. Also, I have to use branded gas. It absolutely does not like mini-mart special stuff. It also seems to like just regular 87 octane as well.

 

MY 4.7 fuel economy went down very bad when cold weather starts... maybe 5 min of idle cold starting or winter gas.....anyways very bad...

 

yeah deffinately hate my MPG in winter they need to do something so mpg isn't so ****ty in winter!