Oil Quicksilver Gear Oil – developed specifically for Mercury engine gearboxes, MerCruiser, Mariner and Force, but it can easily be used for all brands of outboard motors. The only condition is NOT TO MIX with other oils when using it. Don't be put off by the price! There's a reason she's like that. The biggest plus of this oil is, that it DOESN'T MIX with water! Which means, that even if water gets into the gearbox and you don't notice it, the oil will continue to lubricate the moving parts without any problems, thanks to its unique formula and components. Apart from that, there are ultra-modern grafts, which create a protective film around the moving metal parts of the gearbox, which does not break under any loads or high temperatures! Overall, this is probably the best gear oil for engines, ever created! Mercury recommends changing the oil at least once a season or once a year 100 hours of work. If you use the engine in salt water, it is recommended to change it once a 50 o'clock. It is available in 1 liter packs.