Why don't you get an oil analysis done to check for coolant contamination?

Pressure check your cooling system; see if still contains pressure after sitting overnight from last time the engine ran.

Temperatures over 80C slightly aren't too concerning, but coolant loss, power loss, fuel efficiency loss, and white smoke combined are. Typically indicative of a head gasket or head failure.

__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)