Originally Posted by JCL

Seafoam is a blend of oil, naptha, and alcohol. The oil doesn't belong in a fuel system, and can only reduce the quality of a modern full synthetic lubricating oil. The naptha is a solvent, and is often used to make camping fuel (white gas, etc). The alcohol is another cleaner, commonly sold as white-board cleaner and lock de-icer. Interesting that the oil is listed by Seafoam as being between 40% and 60%. Makes me wonder if the recipe varies from batch to batch. Also interesting that the same product (according to the MSDS) is packaged as TransTune. That saves on product development costs, I presume. Just add a new label.

None of the above were designed to be burned in a modern engine, or provide improved lubrication in the oil sump of a modern engine. If you do add it to the oil sump I would make sure to drain it out very soon after.