OIL IN WATER - BrianW
Unfortunately, it sounds like a head gasket.
OIL IN WATER - Armitage Shanks{P}
A quick, and not very expensive, compression check will confirm or deny this. If one cyclinder is 'down' there may be visible signs on the outside of the engine but it may have blown between 2 cylinders so the leakage would be 'internal' and not show outside the engine. E&OE!
OIL IN WATER - Adam Going (Tune-Up)
No such thing as a QUICK compression test on an Omega V6 !! Anyway, if a head gasket has failed between a water way and an oil way it will not necessarily result in a low compression. A pressure test on the cooling system might prove the point, but it has been known for such failures, in the early stages, to only allow oil into the coolnat and not vice-versa, as the oil is at higher pressure when running.

Having said all of that, the most likely fault is indeed a head gasket failure, not uncommon on this engine I believe. Don't risk more serious damage to the engine by ignoring it.

BTW, you might get more response to this type of question in the "Technical Matters" forum.

Regards, Adam
OIL IN WATER - Charlton Heston

Apologies for getting the wrong forum.

If the head gasket has gone wouldn't I be losing water as well?
OIL IN WATER - Cyd
Not necessarily. As mentioned above, the oil runs at a higher pressure than the water so oil may be forced into the water jacket, but not the other way.

When you get it repaired make sure the head(s) checked for flatness. Has the car overheated recently? this is often a precursor to this type of failure. It may be there's been some local overheating in the head possibly caused by a partial blockage of the waterways (maybe caused by scale or corrosion). Make sure the coolant system is thoroughly flushed and replenish with new coolant (this should be done every two years).