That is why I asked the OP to decrease his mileage in between intervals (and then make it cheaper by using dino oil. A proper synthetic with correct detergents will clean it out faster, but I would still limit my overall mileage intervals to half of whatever I was doing before.
I know Valvoline Semi-Synth blend Red Bottle has detergents made to clean sludge from engines.
" Valvoline synthetics are higher in detergents to help clean an engine "
and "There are many different additive formulations that affect an engine oil. Some additives assist the engine with seal leaks, cleaning and other important factors." -Valvoline.com
Usually the synthetic oils will condition any small or minor leaks and eventually they either improve or go away but that was not the case for when I switch to Mobil 1 full synthetic, after three oil changes, the leaks never changed, and I had found what I wanted and went back to Valvoline.