i just had a sun/moon roof installed in my '05 hch and i love the fact that i can crack the thing to allow for adequate air flow and always keep the air on off, except when its too cold; but this is california so it rarely happens even in the rain. the mileage reduction because of air flow is a compensator of course but it is still better then when im using the fans or fan / compressor combo to cool the vehicle...

but i drive with all 5 windows down, even more so now; but this tank is still well over 50 mpg and it looks like i should be able to top 600+ miles on a at-pzev tank of only 11+ gallons.