2-stroke oil in 4-stroke gas?

[yamahauler44]

I heard from a dealer in my area that is a good idea to put a capfull or so of two stroke oil in with my gas on my '99 YZ400 to help increase valve life, ive been doing it for a while and all seems good. has anyone else heard of this?

[99wr400]

Never heard of it. I think it would lean out the jetting, because the oil would make the gas thicker. It doesn't sound like a bad Idea other than the possible smoking exhaust, and lean jetting.

[642MX]

Two strokes use premix.

Four strokes use regular gas.

[Husky_Forever]

In the 90's with Kawasaki racing Baja, they pitted guys racing their KLX 650's as well. Since Kawasaki ran 2 stroke 250's and 500's all fuel was pre mixed at all pits. If you raced a 4 stroke, you had to run pre mix. Didn't hurt them, just smoked a bit. I wouldn't advise long term use for no other reason than why? Steny

[yamahauler44]

thanks for the input, does anyone know if it would effect the valve life?

[biznet1]

I'm no expert, but it seems to me that it wouldn't be enough lube to help, but it would be enough goo to hurt (over time).

[RADRick]

I heard from a dealer in my area that is a good idea to put a capfull or so of two stroke oil in with my gas on my '99 YZ400 to help increase valve life, ive been doing it for a while and all seems good. has anyone else heard of this?

This is an old wive's tale developed back in the days when leaded gas was banned for sale. Since lead helped lubricate the valves and seats, many thought that unleaded gas would ruin their engines. Although they were right, at first, engine technology soon advanced to the point where lead was no longer needed. Some diehards holding on to their older vehicles started putting things like Marvel Mystery Oil and other lubricants into their tanks to help them deal with not having leaded gas anymore. A properly running modern 4-stroke does not benefit in any way from adding oil to the gas, and certainly not in such a small amount. If you want your bike to smoke and possibly foul plugs, go ahead, but it won't do a thing for your engine beyond that.