MPG for my 04 plate ZS180

[SheppeyTrio]

I've just driven from Ilse of Sheppey in Kent to Bodmin in Cornwall which was a 285 mile trip. I filled up the tank before i left and filled it up again when i got here, i used 38.20L. Which if my maths is right, to get gallons i divided the 38.20 by 4.5 (U.K. gallons) which equals 8.48 gallons! Divide the milage by the gallons (285/8.48) which equals 33.61 m.p.g. Does this sound reasonable for a 2.5 V6? I'm gonna re-do the same on the way home on sunday just to clarify the numbers! I had the climate control on most of the trip so not sure if this would make a difference? So i'm gonna keep it off on the way home.