Black smoke would indicate that your engine is running rich, not white.
Is your car running rough? White smoke would indicate water could be entering your combustion due to a blown head gasket.
Check your oil dipstick for any signs of coolant in the oil and go from there.
I wouldn't drive your car under these conditions until you find out what's going on -- serious damage could result if you're getting coolant in the oil (hydrolock, etc)
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi