i have a 1994 C280 95000 miles. I have a slow oil leak from the crankcase to the cooling system. No water in the oil as it is still clean and no foaming in 3000 mi. Using 5W 20 synthetic. In 1000 to 2000 miles i see maybe a 1/8 inch of oil on top of the coolant in the plastic overflow tank. No mixing or foaming it just lays there. Any ideas? Also i notice a slight growl sound when it is cold.