That sludge ONLY accumulates if NON DETERGENT oil is used. High quality detergent oils (with the proper API rating) have been around since at least the early 1950s. That "10%" myth ignores the fact that detergent/dispersants in any oil worth using traps and suspends the "sludge"- - - -which gets drained out with every oil change.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!