Mercury - Premium Plus 2-Stroke Marine Engine Oil Synthetic Blend 858027K01. Overview. When you're heading out before sunrise and that engine roars to life, you want to know it's protected, truly protected. That's where Mercury Premium Plus 2-Stroke Marine Engine Oil comes in. Built for serious boaters who ask a lot from their engines, this oil delivers quiet strength and lasting reliability. You can feel it every time you accelerate, cruise, and throttle down - smooth, confident, and worry-free