I have a 2010 Accord V6 Sedan ExL w/ Nav. It has slightly over 2000 miles on it now. At the very beginning I think I felt the transmission or engine cylinders shifting in or out of the Eco mode. Even if I felt it was nothing substantial. Now I do not feel anything at all, the transmission and the engine works like magic. I love this Eco feature in my car. After I crossed 2000 miles, the oil indicator shows 80% and I am now getting 20+ miles per galloln in city driving. I used to get 19+ when it was brand new. The fuel grade that I use is 88 because we do not get 87 here in southern Utah. The standard grade here is 85 and I always use 88 instead of the 85. I am hoping that the awkward feeling that you are having will go away once you put a few thousand miles on your new ride.