it could be a million things, take a pic and post it...and no, no motor should leak oil if built properly...if it is the head gasket the compression would most likely be low, have you checked the compression at all? what I do to find a ghost leak is get some brakleen and clean the oil from where it is currently...then take babypowder and put it on a towel and pat down the area...then go for a drive, it will be very clear where the oil is coming from now...when you find out let me know and I will help you fix it or do it for you...