My current tire is a 215/60R16. From what I've read from those who checked the TCH is about 3 mph off at 70 mph. That needs to be confirmed (GPS (speed) or milage markers (for distance))

A 215/65R16 tire would read 67.09 mph when your standard tire reads 65.
A 215/70R16 tire would read 69.2 mph when your standard tire reads 65
A 225/65R16 tire would read 68.38 mph when your standard tire reads 65


The last one might be the better choice, other than it's a tad wider and may hurt actual FE. (Actually all of them will hurt the theoritical FE reading as the standard tire is probably overstating the actual FE by 3 to 5 % if the spedo is off by that much).

I guess what you lose in FE (theoretical reading, not actual FE) would be offset by picking up say 1000 more miles or so on your base warranty