I got like 11.5 mpg this tank, or so I thought until I got home and found out I had been leaking the whole way! The freaking pump overfilled my damn tank! That pisses me off. But even so on normal tanks, I usually get like 12 mpg. Don't know how because my engine runs smooth and I am only 2000-2500 rpm when accelerating Max. And yet if I stay below 2k rpm I get just as bad mpg in the tank.????
Around town in the cold weather, that might be the best you'll see.
I find my niner gets best mpg letting it shift around 2300 when accelerating (being too gentle hurts a bit, getting on it harder hurts a little, but a lot less than you'd expect as long as you accelerate to the same speed in the end). However, driving efficiently in other ways (biggest thing is planning to have to use the brakes as little as possible) makes a far bigger difference.
In the dead of winter, I see 11 - 12 around town. In the summer, that'll become 12 - 14. On the highway, I'll usually see around 17 - 20 at 60 mph, depending on wind, hills, etc. Funny enough, the cam helped my highway mpg a little (about .5 - 1 mpg on average), although I lost a 1/2 mpg or so around town.
My best tanks ever were 21.8 once when stock (over 330 miles) with the cruise at 58, mild rolling hills and a slight tailwind, and another tank was 22.5 after the cam (over 70 miles) in similar conditions, except doing 60 (and I think that run is slightly down hill overall). Those are the only 2 times I've broken 20, however.