As Obie says. If it is fuel then it will probably be from the injector hoses, there are still quite a lot of M3W's with the original crimped on fuel hose clamps rather than the screw type that should be retro fitted by now. You usually get fuel spray onto the aero screen when driving as well, followed by crazed screens. If it is oil then it could be from wet sumping blowing out of the crankcase breather into the air filter of a crankshaft oil seal weep, oil coming out of the cambelt cover lower vent hole, neither of which are as serious as a fuel leak.
