AO Platinum Member
Join Date: Aug 2003
Location: London, England
When the oil/water heat exchanger fails it usually fills the coolant expansion tank with oil.
My Fiat Cinq had an intermittent coolant loss over 2-years, which eventually revealed itself as the head gasket but there was never any coolant in the oil because it was just a failure between the coolant and the cylinder. It used to suck coolant in on the overrun... (they way I drive it, it doesn't sit on overrun for long!)
Hopefully it isn't the head-gasket in your case though.
Hopefully the leak will leave traces of coolant behind and make itself visible.
Audi TT 3.2v6 DSG
xAlfa 156 Selespeed sp3 + Brembo conversion
Fiat Cinquecento 899cc