Holy shit. Am I missing something here or do you all have the reading comprehension of 5 year-olds?
OP is not as concerned about gas costs, as he states in BOTH his posts, as he is concerned about range per tank. He has heard rumours of M3s getting only 300km per tank, and would like input from M3 owners as to their experiences. Personally, I can totally appreciate this-- I love a lot of things about my M5 but one of my favourites on a long roadtrip is the 80l tank.
I have never driven an e9x M3 but the tank capacity is 63l so you should be able to draw your own conclusions from people's stated mileage on the various fora...