Went to check oil level on our Eos with 23+k miles on it and found a white foam on the bottom side. Dealer did an oil change at 20k and I checked the level at 21k and the cap was clean. Should I be concened? I know it could be a sign of a head gasket failing or a bad coolant passage in the head or block. I'm not getting any warning lights and coolant level seems ok (I can see coolant in the overflow tank). Thoughts?????