My 06' 4.8is with just over 90,000 miles. I have owned the car almost 4 years and have always seen roughly 390-400 miles on a full tank of gas, but my most recent two fill-ups have only been netting me 315-320 and that is with less than 30 miles left on the tank according to the OBC. Essentially a drop off in almost 100 miles.
My driving habits have not changed. Virtually all driving is around town stop and go. I have not thrown any codes or experienced anything abnormal. Only real change in conditions is the cold ass weather we've been having.
Just seems odd to me, no?