There is no oil or additive or lubricant that will restore an engine. Diagnosis and repair will restore an engine's performance. Rebuilding valves, rings, bearings etc will restore a neglected or high mileage engine. There are many people who really believe that this gas, that oil, magnetic moleculer gas energisers develped by NASA blah blah blah will give better, mileage more power, smooth idle blah blah. The list of snake oil products and there supposed benefits is endless and the only good result is transfer of cash from you to someone else. But hey that's what is supposed to be good for the economy right now. I think you are wise to be skeptical.

There are some excellent products that may extend the life of an engine and in some cases prevent and remove deposits. What problem do have with the engine that you are trying to fix?