Did some number crunching on
The US DoE's fuel economy site on all of my current/previous vehicles..
8 total vehicles, ranging from a 3-speed auto '87 Ford Escort GLS hatchback up to my current '11 Elantra, the average economy is 21.25/29.75/24.25. Compared to the BRZ's 22/30/25, it's startlingly close.
The Elantra is hands-down my best gas sipper (when my daily commute was ~80 miles, I averaged around 43mpg), but I've owned multiple vehicles with pretty much identical gas mileage. (The Escort pushed its ~2500lbs to 23/29/25 and my '06 Cobalt was 22/31/25)
It will take some getting used to, however, to select the premium pump, as all current/previous rides took regular 87 octane unleaded.