On My first tank the computer recorded a 35 mpg with a calculated mpg of 32.5. All tanks since then have gone steadily down with the computer saying 33 to 32 and calculated being about 30. My last two tanks the computer has struggled to read 30 mpg and calculated mpg of 28. I am at a loss to explain this and am very disappointed in this slide into mediocrity. I suspected my mileage was not going to live up to expectations when on a long highway trip I could do not better then 33 at 70 mph. I know mileage drops off significantly after 65. My driving style has not changed and I try to implement some hypermilers techniques when possible. I have not taken this to a dealer yet and I suspect they will say everything is fine.