oil leak is this common

[mds]

Hi i have an e30 m3 i had it serviced 3 weeks ago and moted last week there were no leak at this time but in the last day i have noticed a small patch of oil which looks like it from the sump not sure really i have looked at the engine from the top and its all bone dry, do any of you know where it usually leaks from toward the bottom of the engine it is moist towards the back of the engine???
thanks for any help in advance
mds

[Brianmoooore]

BMW sump gaskets harden with age, and the sump bolts work loose, but the obvious answer is to get under there and have a look.