Oil leaks

[vxr2010]

So on both my cars , I seem to get oil damp patches rather than a proper leak , my monaro diff is often slightly damp , I got the rear main seal done a while ago , my ute got the sump gasket done , now a damp area looks like the rear main , is a damp patch normal with these cars ? any others leak watching as I can best describe it , with the change in mot rules it’s now more relevant , thoughts ?

[SturdyHSV]

Rear main is a common one, but normally so minor it's only worth attending to if doing clutch or slave cylinder at the same time.

General suggestion is to give it a bit of a wipe / clean up underneath and check it again after a drive (ideally in the dry...!) and see where any new oil has come from. If there's not enough to show up, then just give it a wipe before the MOT as well