We recently got back from a 2800 mile trip. Our v now has 10,600 miles on it. We have been averaging 41mpg until the last two tankfuls. For some strange reason we got 34.5 displayed on our last tank, 32 actual, and right now after 90 miles we are showing 30.5 displayed. My wife drives the car 98% of the time, but even when I use hypermiling techniques the car is not yielding the past displayed results. We are about to take it in for the 10,000 oil change. We live in Texas so it is over 90 everyday, but we keep the temperature on 76. Our driving habits have not changed at all. Any Suggestions?