Usually the MB manual says to open the oil filler cap so it will drain faster and better.... more flushing effect...

Are you not changing the filter .... ? That 8 qt quote may put you a quart OVER FILLED... I don't know about your car...

Like Larry B says.... change your oil when the engine is hot....you get better evacuation that way....

Will you be draining your oil cooler ?

That blanket statment of 8 quarts without asking these other questions is potentially dangerous to your car......