Mercury - Quicksilver 10W-30 Full Synthetic Marine Engine Oil 4-Stroke Series Full Synthetic 8M0175781. Overview. There's a certain comfort that settles in when your engine sounds exactly the way it should. No hesitation, no roughness - just that smooth, steady hum that tells you the day's going to be a good one. Whether you're running out to your favorite fishing spot or easing back toward the dock with the sun dropping behind you, having the right oil in your engine makes all the difference. Q