[MetroMPG]

Welcome!

I'm going to guess by your numbers that you're doing either mostly highway driving, or you're already using a number of hypermiling/ecodriving techniques (because the cars aren't capable of 48 mpg(US) on their own in what I'd call "normal" sub/urban driving).

(You are talking in US MPG, right?)

If you're doing mostly highway driving, unfortunately these cars are not as forgiving as others in terms of the speed at which they achieve their EPA highway rating in warm weather (right around 100 km/h / 60 mph). Most other cars I've driven get significantly better than their hwy rating @ 100 km/h.