Mercury - 80W-90 Premium Gear Lube Outboards and Sterndrives Marine Formula 858058K01. Overview. There is a certain peace of mind that comes when your gear just works - no grinding, no slipping, no surprises. That is the kind of trust Mercury 80W-90 Premium Gear Lube gives you every time you shift into gear. Whether you are cruising out for a quiet morning or pushing through heavy chop on the way back, you know the lower unit's protected. It's that smooth, steady performance that turns a boat ri