I use a oil measuring jug and put in one and a quarter of thinners like petrol, diesel, heating oil and add waste engine oil up to the five litres or us quarts mark.
Just give it a quick stir and tip in.
The oil is just filtered with sock filters.
I think that because the oil is black you just think its dirty,so when you can remove that preconception from your mind its not a big deal.
Removing the bung and cleaning the carbon that sits behind it is the only extra thing to do,if not it brakes off and the engine makes a nasty knock until it clears.
When I pull the engine apart next time I am going to set the bump clearance to that of a 8/1 and fit the appropriate bung so there is more clearance between the piston and the head for loose carbon.