BRAVO... Well written response... I have used MMO in all my race cars for 20 years... These are some internet quotes from well informed engine specialists.

Marvel Mystery Oil "combats internal motor rust and corrosion, lubricates valves, piston rings, upper cylinder walls, and eliminates valve sticking. Keeps rings free and reduces piston and cylinder wear. Also keeps fuel pump and carburetor parts clean, eliminating the need for frequent adjusting. Marvel Mystery Oil retards formation of power dissipating motor deposits, such as gums, varnish, and sludge."

The TCP/Marvel Mystery Oil option: These are most likely about the same thing, with small changes in the recipe, so as not to infringe on another's copyright. Both are high in detergents to do the cleaning job. Neither should be used for the first time on a high time engine; about half TBO or less should be the cut-off time, for first use.

IN OIL SYSTEM
Use one pint Marvel Mystery Oil about 5 hours before oil change. If screen type system, be sure to clean screen. Then, in the new oil, install one-half pint MMO. This cleans the carbon and sludge collected in the engine passages and crevices and hydraulic lifters, and stores it in the bottom of the oil kidney. Some will make it to the screen, but either place it will be removed at oil change.

IN THE FUEL SYSTEM
Use the directions on the back for amount to put in the fuel per gallon of fuel (4 to 6 oz. per 10 gallons of fuel). MMO goes through the carburetor as a droplet, broken up like the fuel. When it enters the combustion chamber and the gasoline ignites, it is vaporized and soaks into the carbon buildup on cumbustion chamber walls, valve guides, around the valve stem, and on the spark plug. It soaks into the carbon and eventually loosens it up and it goes out the exhaust system.

Now you know how it works, I will neither recommend or not recommend the procedure. Like Fox News says,"I report and you decide". I do know it will help when lifters start to be lazy and not do their job. When valves are beginning to stick, it will free then up. Some people swear by it, some people swear at it, but results is what really tells the tale.