42 odd mpg on m/way but to get that i had to do 60 mph.Doing 70 gave me 37 and 80 dropped it down to 32 but i dont rely on the MFA.
Most accurate way i know is to fill car up,do 100 miles or even 200 and then refill from same pump,same garage and then calculate how much fuel it takes to refill.Work from the first "click" and push nozzle right in.