In reading your other post about the tube issue- you state that this unit was purchased at auction about a year ago. Given that info- if the unit's last life was subject to multiple cold starts throughout it's day that would certainly account for the milky engine oil.

With that said- it might take numerous oil changes to get all that sludge out of the engine. As was previously stated- replace the engine thermostat, use thin engine oil -10w- & let the engine run (about 1,000 rpm) until the oil starts to look milky again. Then change oil & filter & repeat- complete this cycle until there's no more milky appearance in the oil after it has been run for a while.