C280 coolant in oil

[srusso]

I have a 98 C280 with 150K. I got a low coolant warning.added about 1/2 gallon and 2 weeks later it was low again. I dont see any external leaks. The oil filler cap is white and milky looking. I looks like there is specks of oil in the fill tank.No sign of smoke in the exhaust and the temp is good. I read some of these cars have an oil cooler at the filter but i dont think mine does. i dont see any hoses. Might there be one in another location ? Is there one built into the radiator? Any ideas where the coolant is crossing into the oil? Thanks