Iv used mmo in my high mileage Burb many times. I also had a tap when I first got the truck almost ten years ago. Open the label and theres some very vague instructions.... when it was tapping I would add something like 1/4 quart, drive the truck for a week and then change the oil. It was messy terrible oil changes. Eventually the knock went away and the oil changes were normal.
Iv made this a part of my routine maintenance every spring. My engine is all stock and never been touched. Purrs like a kitten and gets right around 17 miles/gallon.
Iv only used seafoam in my 10hp 1963 johnson outboard motor when it was acting up. I mixed it up in the gas to its max dose and it made an instant difference. I was burning regular non ethanol gas. this engine sat in a basement for 30 years right after it was professional maintained. It started on its first pull. Now I cant find regular nonethanol gas and burn supreme in it now, it runs just like that day when I put seafoam in it, just like a top, best it's ever run.
Those are my only experiences with those products.
Al