Mercury - 25W-40 4-Stroke Oil Change Kit L4 Verado Series Marine-Grade Components 8M0188358. Overview. There's something grounding about doing your own engine maintenance - that quiet hour in the driveway or at the dock when you're taking care of the machine that takes you out into open water. Changing the oil is one of those moments that makes you feel connected to your engine. You're giving it what it needs to stay strong, smooth, and ready for whatever the day brings. With the Mercury Marine