Redd

"the Outback feels like a Porsche "
Or perhaps a Karman Ghia?
Everyone agrees that the Subis, all of the Subis, with the stock base engine crap out around 40mph and then run out of power. Now, if you stick in a bigger optional engine...that's another story. Or maybe they were thinking of a Boxster, isn't that the one where the back spark plug never gets changed unless you hoist the engine?

To the OP, what you call winter gas is probably ethanol E-10, which is widely known to kill 10% of your gas mileage on most cars. And while the newer Q5s have "flex fuel" engine systems that are supposed to compensate better for that, ethanol still is a lousy fuel for gasoline engines.

I'd look for comparisons strictly on the highway in order to get more objectivity into things. "City" driving means nothing, it is different for everyone. Cruising on the highway, with a damned good foot or cruise control, will give you a highway MPG number that is the only fair thing you can compare to anyone else's highway MPG number.

If your highway MPG is the same as others, there's nothing wrong with the car. If everyone else is getting 25 and you're getting 20...Yeah, it is that simple, there's something wrong. Computers, sensors, brake drag, bad engine, a transmission that costs more than any Karman Ghia ever cost, too damned many things can be wrong but first, you need some objective numbers to see IF anything is wrong.

Steppenaudi

Hills suck w.r.t. gas mileage. Especially in urban environments. Flat landers will get much better mpg than hilly dwellers like here in Seattle.

Dalancroft

VERY hilly in my neighborhood -- lots of 15-18% grades. That's probably not helping!

Will do a check the next time I do a long freeway drive (via computer). Maybe I can bump up to 23-24-25 mpg.