BG engine Flush
Pour in run engine for 10 Minutes at 2K rpms, drain. Then take a air hose and blow air through the center stem on the oil filter port. pushes out oil in oil pan and lifters... Usually get .5-2 quarts more oil out.
Refill engine with 6 quarts of oil. disconnect injectors crank for a few minutes to prime oil system.
Reconnect injectors drive for 1K miles and repeat.
Done this on a very poorly maintained nissan frontier mountain of gunk in the valve covers, it looks like a soso maintained nissan now. and it doesn't burn any oil.
I do have a pressurized oil injection system that I can pump oil into the lifters after I have purged the engine though.