28.5 MPG average over 20,000 miles. 60% Hwy.
On the highway my car gets the same MPGs cruising at 50MPH as it does at 65MPH. It does get a little worse above 65.
Whether on the freeway or in city driving, the trick for me is to maintain momentum and use the brakes as little as possible. Never come to a complete stop if you can help it. It's easier on your clutch too.
It's amazing how little you need to brake if you look way ahead and adjust for what's happening in front.
The brakes and clutch on my old 2003 WRX are at 100K+ and still ok.