I recently replaced the worn tires on my 2015 FFH with exactly the same tires (Michelin Energy Saver A/S - P225/50R17 93V). I immediately noticed a drop in gas mileage of 2 mpg or more. Have others noticed this?
Remembering back a bit, my gas mileage used to be more like what I'm getting now, but in the last year (less?) my gas mileage increased by 2 mpg or more. Therefore it makes perfect sense that after installing new tires, the mileage would drop back to its "old" numbers.