Does anyone here remember some stuff called "motor honey"? This was a "fix all" for old, tired motors. All you did was pour this goop into your engine, and it immediately quieted things down. And it actually worked, kind of....! Turns out, all it was was 80-90 weight gear lube. It raised the viscosity of the oil because it was so thick.
Suddenly you had- quiet mains, less valve train noise, more oil pressure, and increased compression and it slowed down oil leaks. Until the engine got good and warm. Then you had nothing.
But unscrupulous auto dealers bought this stuff by the 50 gallon drum in the 70s.
These are the same guys who also packed the rear differential full of sawdust because it stopped the whining noise a limited slip made right before it went "boom".
There is no "cure in a bottle" for an engine, no gunk in the world is going to magically fix warn out parts. Brand new oil used often is the best medicine, and lots cheaper then a rebuild (or slick 50).
Lee