Honda USA 2011 CRV recall fix robbed 20% fuel economy. Torrance, California

I have a 2011 CRV with 24,000 miles. (I drive 80 miles a day). In November 2011, I had a software update from a recall  that adjusted the timing. I was getting 32 mpg consistently on the hwy, and 28 when I did city driving. After the update,  the best I get is 26, city or highway. Honda corp said to have the dealer check it. They did, and all was ok as far as they were concerned. Then Honda said to have the dealer run a mileage check. The dealer said there is no such thing, other than looking at the mpg indicator when they take it for a drive. Then Honda says if it is within the "normal range", then there is nothing they can do. No one can give me a number for "normal range". I keep getting the runaround from Honda. I have the extended warranty as well. I have tried a higher grade of gas, and a different gas station, but I have seen no change. I drive the same highway every day. This software change will cost me over $900 a year at today's fuel prices. The person I talk to at Honda is rude and just keeps saying there is nothng they can do!
Peter, Gloucester VA.