Do you think if the outside temperature is 30 celsius, the car will cool better if you use the AC on 14-16 or 18C? LOL...read about air cons...Just a note to Honda, on the 9th gen you need the air con to go lower ie down to maybe 14 then low instead of the current 16.
I often find 16 too warm but low too cold. It would be good to have something in between for those warm but not scorching days.
I find my 09 1.4 the same on hot sunny afternoons when the car has been standing in the sun only that there is a 2-3 mpg reduction, probably down to the engine.I've said before, the AirCon on my IS200 used to obey the temp you set and it soon got down to that temp and kept it there. If you set 21°C you got 21°C.
I find the Civic has to be coaxed down to the required temperature by setting it super-low otherwise the fan gives up half way there and no more cooling.
I did a journey of about 100 miles earlier in the year after the Civic had been sat in the sun.
Starting inside temp was 45°C and even after 100 miles the inside temp only got down to 26°C with it set on 20°C. On hot days when I'm at work it starts out at about 20°C because it's parked in an underground car park and even with the sun belting down, on the journey home it manages to keep it at about 22°C.
This is probably why the MPG hit is almost negligent because it's not very powerful.