I've had boats & motors for years, some really old and some newer ones. I used SuperTech lower unit oil in all of them and I never had a problem with this oil. My first motor froze & broke the housing in the winter because of water in the lower unit. Since that day, I drained the lower units in the fall every year before the freeze here in case there was any water in the units, and refilled them right after draining them. The old oil looked like new every year and never had a gear problem. I would suggest changing oil in them before winter storage if you live in a cold climate. I learned the hard way, so I am passing this along to you.