i thought about that, but the thing is, its been cool, i have ventshades,so generally i leave the windows cracked with the a/c on or off and just adjust the temp to suit me ( i like the fresh air) .. Soooo , while buffeting may have had some impact, i really dont think it was enough to explain the differences. no real major changes in my driving habit/configuration this time of year. in fact, ive had the windows closed and ac off this past tank, as its been cold , and again, worse milage than when its on.. i drive over 600 miles a week just commuting to work and back, so i can test this again in no time..but im due for a mobil one change again in a few days, and an k&n "wash" so ill let the truck settle in again after that before i report back on this..