My mileage has been terrible lately. I've been having trouble keeping it above 35mpg, and all of a sudden I'm working on a 33mpg tank. I think part of it is the cold weather and the other part of it is the winterized gas formulation. The best I could do this morning was 33.9mpg on the way to work. Afternoon segments are barely reaching 35mpg. And I don't even want to talk about my last highway trip.
I have been getting better mileage with my Yaris using 1/3 to 1/2 throttle (shifting at 2500 rpm) than I did using 1/10 throttle. It could be that my skills are improving and my engine is breaking in, but my last tank was over 49 mpg for city driving. If yours is auto it may not be possible to use 1/2 throttle at low RPM.
I got a tank of ethanol blend and it's getting pretty cold here so my MPG is about to take a dip I suspect.