I recently did an across country trip in a 2008 miata 5spd at more than legal speeds and was absolutely amazed at the kind of mileage that car is capable of at higher speeds. I fully expected it to suck so badly at interstate speeds...but once out of VA I almost never ran under 80 mph. To do so, would have been my undoing. I would have been roadkill for sure. Seldom did I exceed 90 mph. But even at those elevated speeds I still managed to average over 30 mpg overall through every kind of weather we have except snow. Thank God for no snow. I also discovered once I returned home with the car, it runs very nearly as well on regular fuel as it does on premium and gets just as good a mileage...guess what I am running in it now?
yeah you got it. Only car in the fleet that consistently returns better than 30 mpg no matter how I drive it. That said, I still like my gas guzzling subarus.