All 3 cars currently in our driveway average ~28. One is a compact car (Mazda 3). 28mpg is not great for a car that size/weight and the newer ones are more efficient. The old Mazda 626 is midsized...28mpg is pretty average for a car that size (both Mazdas have 150-160hp). We have a 4-5 year old Toyota Rav4 that is significantly larger and ballsier than the Mazdas, but the mpg rating is about the same.

18mpg isn't even close to average. Not when there are a lot of non-hybrid, non-diesel cars on the road getting at least 2x the mpg. Perhaps if one lives in an area where everyone drives large SUVs and pick-up trucks 18mpg might be average.