Without pointing any fingers, one of the biggest factors in a vehicle's mpg is the driver. I routinely get over 21mpg in my 2011 4WD SR5 with stock everything in a mix of city and highway driving. If I really try to maximize mileage and manage to avoid heavy traffic I can get up to 23.5. Yes, that's higher than the EPA estimate and no it's not a typo. And this is over several days, not just a one-off thing where you drive downhill with a tailwind. My wife usually gets between 17 to 17.5 in the same vehicle burning the same gas.
I'm not a hard-core "hypermiler" (I drive an SUV, not a sub-compact), but I do use
some of the same techniques:
How to Hypermile (with Pictures) - wikiHow
The main difference is hard acceleration away from stops (
she can't stand it if someone "beats her off the line" or passes her in traffic, but I don't care), max speed on the highway (
she has blonde hair and boobs to help get out of tickets, but I don't), and idling the engine while stopped for a long time (
she keeps the AC running while idling, I roll down the windows with the engine off).