Detergents and Solvents
Many of the older, better-known oil treatments on the market do not make claims nearly so lavish as the new upstarts. Old standbys like Bardahl, Rislone and Marvel Mystery Oil, instead offer things like "quieter lifters," "reduced oil burning" and a "cleaner engine." Most of these products are made up of solvents and detergents designed to dissolve sludge and carbon deposits inside your engine so they can be flushed or burned out. Wynn's Friction Proofing Oil, for example, is 83 percent kerosene. Other brands use naphthalene, xylene, acetone and isopropanol. Usually, these ingredients will be found in a base of standard mineral oil.
In general, these products are designed to do just the opposite of what the PTFE and zinc phosphate additives claim to do. Instead of leaving behind a "coating" or a "plating" on your engine surfaces, they are designed to strip away such things.
All of these products will strip sludge and deposits out and clean up your engine, particularly if it is an older, abused one . The problem is, unless you have some way of determining just how much is needed to remove your deposits without going any further, such solvents also can strip away the boundary lubrication layer provided by your oil. Overuse of solvents is an easy trap to fall into, and one which can promote harmful metal-to-metal contact within your engine.
As a general rule of thumb these products had their place and were at least moderately useful on older automobile and motorcycle engines of the Fifties and Sixties, but are basically unneeded on the more efficient engine designs of the past few decades.