ORIGINAL: countilaw


Have you owned or run a YS engine? They are NOT like other model engines on the market. They contain silicone parts inside the crankcase that will be destroyed due to petroleum based products. We are not referring to fuel lines or carb o-rings. A tank pressure fed YS engine has fuel pressure regulator built into the crankcase that contains a silicone diaphragm. It will come in contact with anything that is injected into the crankcase. It will then swell and cease to function properly.
Using your MM oil in standard 2 strokes and 4 strokes is just fine, lots of folks have done it for years. YS's ARE NOT STANDARD ENGINES!!



Four Stroker, I have to agree with you. It's really something to see so many self proclaimed experts with all this advice that they have little or no knowledge about.

I ask, are there ''o'' rings in the fuel injection system of a car? Are there rubber, silicone seals, or diaphrams in a automobile transmission?

Now I ask, are there ''o'' rings in the crank case, air passages and combustion chamber of a YS or any other 2 or 4 stroke engine? Did anyone say to run the after run oil through the fuel lines? Does Castor Oil have rust inhibitors in it? Does Castor Oil gum up after sitting up?

Everyone has their own formula for making after run oil. From mixing ATF with Castor and ATF with Mobil One.

Marvel Mystery Oil has been around for a long time. Ask the owner of a 1939 Cub if he uses Marvel Mystery Oil in his fuel and oil? 9 times out of 10 he will say that he does.

I've got engines that I am still flying that were made in the 70's. Still running strong and all had Marvel Mystery Oil used as an after run oil.
So, If they have lasted this long, then I will continue using Marvel Mystery Oil.

Maybe it's disolved all the ''o'' rings in my crank case. Because I haven't been able to find any in there.

Frank