Mercury 858026K01 Premium Plus 2-Stroke Marine Oil Mercurys Premium Plus 2-Stroke Marine Engine Oil is formulated for todays high-horsepower outboards. This oil has a higher concentration marine additive package that meets the needs of high-horsepower outboards including direct fuel-injected engines in extreme marine operating conditions. Premium Plus far exceeds Mercurys in-house test standards, which are more stringent than the industrys TC-W3 standard. Premium Plus has a clean burn, reducing