I have never owned an M3 so i cant comment on the jump, although i drive an Avant currently and my friend has both an e46 and new V8 M3 so i could comment a wee bit about running costs! First off, this car has the biggest range of figures of mpg depending on driving!! Bottom line is out of the 3 the avant is the most thirsty! The v8 m3 isnt far behind and the e46 is the most economical! I find when starting from cold when the choke is on in the mornings it really eats the fuel. When pulling out of the house and heading up the road it reads between 12-16MPG. In town collecting kids from school and town driving etc. its down around 12. However, on a long run cruising at 60mph i get 25 which is really good, and pushing that to 80mph on the motorway gets about 22-23. the lowest i have had was 5.9mpg when in town with some colourful acceleration! ahahah the average for the car is 20.1 ,if you do alot of city or town driving you would need a BP lorry coming after you!! i hope that covers a wee bit of what you want to know! Other side of the coin is that once the foot goes down and you hear that V8 and you're being hammered into your seat it becomes all ok! Get a drive in one... it'll probably win you over....