Finally, the detergents work to clear sludge and gunk out of ... high-mileage engine. Spending a few extra bucks per oil change on high-mileage oil is way cheaper (and, honestly, smarter) than ...

Two things I would try: There is a new oil (I have not tried it yet) from Valvoline called Restore & Protect that is supposed to clean the engine and remove carbon that may be keeping the oil ...