tell your buddy to change the jetting on his RM and stop blaming the premix oil. Once you have the jetting set correctly you should never foul a plug. I had my last bike for 8 years and only fouled a plug when I first got it before I corrected the stock rich jetting, after that, never again.my buddy runs it in his rm 125, has a nice smell to it. It fouls plugs alot,