Mercury - Quicksilver 15W-50 Full Synthetic Motorcycle Oil Engine Lubrication & Protection Full Synthetic Formula 8M0128375. Overview. There's a special kind of satisfaction when your bike feels strong and steady from the moment you fire it up. The throttle responds cleanly, the engine sound settles into that confident growl, and every shift feels smooth and deliberate. That kind of trust doesn't come by accident - it comes from using the right oil, the kind that's built for heat, high revs, har