it seems to make sense that draining the oil cold after all the heavier particles settled in the bottom is the way to go. Modern syntethic multi viscosity oils have no problem with slow flow rate when draining out without warming up the engine. This is also a safer approach.
An Engine Oil is technically called as the "Blood of the Engine"
Engine Oil has two primary tasks to do in every engine.
To cool the engine.
To reduce the friction between the components of the engine. Thereby enhancing the the life of the engine components and thereby reducing the wear and tear in each and every components of engine.
Coming to ...
Because anything which could be said here as an "answer" is a guess, here's what I got for you. It would be my best guess there's an issue somewhere in the valve train and its wearing out. Most likely something is happening with the lifters and/or camshaft. It might also be there's an issue with the rocker arms, but less likely. My reasoning behind ...
Pump it out.
You can get electric or hand pumps, ones that are already built into a tank or ones that are just an inlet and outlet hose.
It wont get all of the sludge out but it will get more oil out than draining from the sump plug will. It is time consuming at best so I've only done it a hand full of times (twice on a car with a rounded off sump plug and ...