I too have changed for mpg reasons, but only because there was a 20 mpg difference in what we should of got, and we are a couple that are normally able to break manufactures mpg quotes when trying, merc b180d claimed at time was 58mpg we got 68mpg pump to empty to full to empty runs, bmw 120d old one we claimed was 62 for xdrive and we managed 66mpg with same test.. bwm 318i estate 1.5 petrol claimed was 52mpg the most we could get was 34mpg worse that when we had 2.0 version we had as cover for weekend which got us 45mpg lol… so we changed and got tiggy, 2.0D thats bad though still as max is 42mpg rather than claimed 52 but considering its almost twice the weight as the 318i estate, thats a whopping 10mpg more and its got 50 times the kit as std… hoping next time round to get a hybrid of some sort as the only decent all electric range on scheme is they hyundai and the price of that is too rich for my liking.