I have noticed this aswell, thought it was too good to be true and it is! 3-4 mpg out as you say, just done a gentle 160 mile round trip (75-80) on dual carridgeway/motorway and ICS shows 31.5, this will be about 27-28 i reckon when i work it out for real which without going really slow is the best you'll get i reckon. I'm averaging about 25 (real mpg) so far, similar to the 2 guys at work with M3's
