Drive like only man really really old man. Right now sense the s475 over stock just got tuned. it's prolly right around 12-13 still in the first tank of having this setup. But man it runs great next tank I'll go back to old man driving and I'll report back!
265/60r20's, ccsb, ppei tuning. 13-14 city, 16 average town cruise, any stretch where I can hit 40+ and I see anywhere from 18-22 conditions/temp/fuel dependent. My hand calc average highway is 20.3
Average is around 18.5 using Fuelly App. I drive 25 miles each way to work on rural roads. Went to Gainseville, GA last weekend and averaged 16.1 going there at 80-85. Slowed down to 75 and got 20+ mpg on the way home.
The sweet spot for mileage is about 70. I'm running around 1600 rpm.
I usually run about 60 on the country roads and pretty much drive like an old man because I can.