So this brown is sludge/carbon or varnish?
The posts above says seafoam but I have my dislikes on that product. Sounds like you are using a dino oil, based on your posts..tisk tisk! :)
Sounds to be your have a dirty engine and the oil is std. If you used a synthetic (group 4 or 5) based that would suply some cleaning; aka diesel oils. What I like for an addative based on my testing, great customer help (UOA house like it) is Lube Control Lc20. The stuff has been out for years and it works mint. It is not a flush and takes some miles to work and works very well. Try it out. They are some others but customer service is poor along with other things...
What I would do, this is me, is spend the $$$ and pull a test. Maybe you are a parts not working as it shoud (more fuel in oil, wear (from cams, rings etc) is though the roof (brown stuff you see?), engine oil is not working good enough.....
Lc20 would clean, a HDEO would, along with others. YMMV
My engine is clean though. :P :P :D :D