My wife's 94 Cutlass Supreme S 3100 V6.
The car sprung a coolant leak from the by pass hose this weekend. Easy fix, 5$. However, when I was poking around I noticed a little bit of oil in rad on the top of the coolant. The overflow bottle had what looked to be a lot of oil in it. From what I can tell the cooltant temp does not seem to be different than normal. The oil itself does not look milky or foamy.
I was thinking a head gasket, but if it was I would think the car would be over heating. At least my Laser did when it blew head gaskets, now I do not know. A search found mention of an intake gasket.