What's EO? We only have E-10. I'm not sure about Yamaha but Suz factory oil had ring guard in it. You Do Not want to put more in. That stuff works!!! She will burn out all the carbon in the cyl. I just checked and Yamaha 4 stroke oil does have it in the oil. Be careful. My Suz mechanic told me this when I bought the motor. He said he is finding 4 stroke motor will low compression. When he asked the customer, they say they been using ring guard in there gas tank. Yamaha 4 -stroke. @@@@ using a proprietary blend of marine oils have -specific anti-wear additives, shear-stable polymers, corrosion inhibitors, detergents, dispersants and viscosity index improvers. In short, they’re far superior to automotive engine oils in their strength of protection@@@@