I have some 2-stroke oil that has been sitting in my injector oil tank for 12 years something like that. I believe it was Honda gn2 injector oil while Yamaha dealer was closed at the time I believed so I got that stuff how long can it sit in the tank and still be good I don't know if it's semi-synthetic but I am assuming it is.it did have access to the atmosphere through the breather pipe but the bottom of the tank had a screw and rubber hose in the bottom.do you guys think this oil would still be good even though the bike has not been subjected to direct rain or anything like that.

I'm not a petrochemical chemist, so just my $.02, for what it's worth...

It's probably fine, especially if it's not a 'bean' oil. But oil is so cheap, I'd just drain and fill with new. When I was a kid I'd leave the oil in the injector tank over the winter, never caused a problem. 12 years is a looong time though.

I've read that typical motor oil has about a 5 year shelf life. Don't know if thats true.

If your talking about the shelf, the way I build things the oil will outlast the shelf.

Thank you guys very much for the info. I guess I will drain it just to be sure. Time to get the proper oil for my Yamaha the Yamaha 2s.