The automatic gets better mileage than the standard. How much better I don't really know. My perfectly honest mileage is typically just under 16 mpg for in town with lots of stops, traffic lights and low average speed. I have gotten 17 mpg mostly on the highway plus some around town driving. Never have gotten better than 17, but I also have not taken any road trips so that is an unknown. I expect I could get it up to 19 or 20 on the highway. My FJ is auto 4 x 4, roof rack, rock rails & stock tires. No other mods that would affect mileage. Some of the guys here are reporting 22 or 23 mpg on the highway and 19 around town or combined driving. The main reason my mileage sucks is because I tend to goose it more than I should. It's fun, but expensive fun these days!
My mileage still sucks when I try to drive very conservatively, so finally I just said **ck it and don't worry about it. I'm confident that we will soon annex Kuwait and be good to go for a few more years.