Mercury - Oil Change Kit, 25/30HP EFI FourStroke, 2 Liters Maintenance 8M0081911. Overview. These small 25 and 30HP Mercury EFI FourStroke engines may be light, but they earn their keep. They idle a ton, jump into throttle without warning, and get hotter than people think on long runs. Fresh oil makes a big difference in how they behave. This kit keeps the job simple-two bottles of the right oil, the correct filter, a new drain plug seal, and a little drip tray so you're not wiping oil off the m