So this past weekend me and the wife went to panama city for a little get away. We also were joined by my brother and his girlfriend.
I broke down and took the Mazda 3 there. I love to drive my HHR but didn't want an extra 1000 miles on my HHR.
We figured that with four people and luggage her Mazda would get about 27-28 mpg. It's rated at 22 city and 29 highway.
Well we were pleasantly surprised at the first fill up when it got 31.1 mpg. That was on premium fuel. On the second tank, on the way home it got 30.9 mpg on regular fuel.
So I now know in her car it don't mean jack squat what grade fuel goes in it.

I was very impressed with the mileage we got. The HHR probably would have returned about 32 mpg.

It was nice to come home and know that we didn't put any mileage on mine.