Mercury - Mercury 10W-30 4-Stroke Mineral Marine Engine Oil, 1 Quart Marine Engine Oil Mineral Blend 8M0078625. Overview. Every boater knows there's a certain peace you feel when your engine starts clean and settles into that smooth, steady rhythm. It is the sound that tells you the day is off to a good start and the water ahead is yours to enjoy. Mercury 10W-30 4-Stroke Mineral Marine Engine Oil, part number 8M0078625, is one of those behind-the-scenes essentials that keeps that confidence aliv