It does seem an anomaly at first glance,cars are without doubt more economical than they used to be,and they have similar emissions add ons to tractors.But tractors are much heavier,maybe even double the weight of say 25 years ago.Stockmans MF 390,2wd would be 3t? todays equivalent 5612,maybe 5t.Nearly all 4wd with air conditioning as standard,not to mention powershift and vario transmissions which are bound to use more fuel.There is a bigger difference between brands than there used to be as well,some of them use fuel to burn off the soot for example