A fuel additive cannot put a coating on the chambers, as that would be strained out by the fuel filter, unfortunately.

There are ways to coat the pistons and chambers. Ceramic coating. Some racers do this, but it's very expensive and requires you to take apart the engine and coat each item individually.

There's no way to get a working coating on the engine with parts moving at over 3000 rpm and under load, with fuel, air and carbon swirling around in those chambers. At best, it'd be uneven, flaky, and it might possibly chew up your exhaust valves and catalytic converter on the way out.

You can ask at the demo: "Sir, how many companies apply teflon to the pan while the customer is frying eggs at the same time?" The answer should be enlightening.

The first link I posted has sub-links to testing results which show that the MPG Caps are merely octane boosters and contain nothing else of any sort. Here:

http://powermagic.myffi.biz/en/pdf/s...estresults.pdf

I don't know if cutedoc finally tried them, you might PM him and ask for his results.