Vehicle in for oil change; discovered oil in radiator overflow tank.

For about an hour I thought we had nailed the problem based on your answer to my question. However, in talking to my mechanic again today, here is the scoop. The radiator overflow tank has ENGINE OIL in the fluids, not transmission oil. PLEASE ADVISE, THANKS.

Well that's just not indicative of the 3.1L engine .. I suppose it's possible but the 'many' I have repaired over the 'several' years i have been been in the business, it has always been transmission fluid from a failed cooler inside the radiator .. I will add that it's hard to distinguish the difference between trans. fluid and engine oil when it's mixed with antifreeze .. At this point, I'm out of ammo... Good luck with it!

Sent another comment this AM re the above question. To give us a little time for decision making, is there any advantage in having the cooling system flushed?