Have used Marvel Mystery oil for years. Works in my old flat head motorcycle. Keeps the Ex. valve guide happy. I use it in an old craftsman "squirt" oil can to reach into places with a bit less mess. But my best use has been at the drill press. It cools the bit and....it smells good. Seems to make drilling more efficient but that could be wishful thinking on my part. It works as a penetrate and likes heat. At least as long as it is not too hot. Works for me. For the other "additives" that I have tried...Not so much. If you want to remove carbon from an old engine, this trick I learned from an old guy here in Utah. Warm it up, get a good high idle speed and pour a little water right in the carb. Keep it running. Steam breaks the carbon up and it comes right out the tail pipe. Works like a champ! Water to steam = 1800 to 1 expansion. That is what blows the carbon off the pistons. Got to keep it running cause it can be a pain to get started if it gets too wet. Works on tractors, military trucks and my 235. Cost...a glass of water. Or if you have to be a big spender use bottled water.
