I run 160 degree thermostats on my old MoPars. I have one in my 51 Plymouth that I rebuilt the engine back in 1968. It has about 70,000 on the engine. There is no sluge in the tappet chambers as about a year ago I did a valve adjustment on it. I do/did change the oil on a 3000 mile schedule and always used the same brand oil. Most all of my vehicles have rebuilt engines, and no sludge in any because of good oil changes and using the same brand of oil each change.
I don't worry about the 160 degree thermostat and sludge.
Bob