My auto 22re gets 20 in the city with some highway and 23 or a little better all highway this time of year with temps in the 60's to 80's. In the coldest part of winter here, 10 to 20 degrees, I was getting 17 or 18 in the city, and 19 or maybe 20 on the highway. The mileage I am getting now is just after a new timing chain, and head cleanout, new valve seals, etc. I also have all my emissions equipment installed.
I still say there is no reason to poison the air, even if you decide to eat an owl or two, while dreaming about running a two stroke motor in your next truck. Just think of all those children suffering from athsma, while chopping down the tallest redwood you can find, and consider using a catalytic converter. thanks