Is all lower unit oil basically the same ? For my 25 Mercury.
Boats & Motors
oil
Any outboard manufacturer's lower unit oil will work well.
Agree with everyone's comments, such an easy thing to do, especially given the cost of lower unit repairs.
I dont think synthetic will do any good. Synthetic shines cause it can take a lot of heat before breaking down. I dont see the oil getting scorching hot from being in the water all the time . I have forgetten to change the lower unit oil some years, but it is so cheap it is foolish to not do it every year. My 25 takes about 8 oz. or so.
It’s only a 25, as long as you change it every year anything is fine. However, as has been said, those small engines take such a small amount of oil that it really isn’t much more just to use the the good stuff and have a little better protection. Quicksilver should be your cheapest OEM receommendation.
One shot, I have a 1997 25 horse Merc. I have used everything there is as long as it is lower unit oil that is 80/90?. I was told to use Merc by the Merc dealer , (of course) so I mainly use that. I have also used the cheap Fleet Farm ( Shipmate) and the dealer said it was poor quality. SOme years I didnt even change it ( foolish) but now I use Merc and sometimes Amsoil. If I can keep it from overflowing , it is only about 8 oz. of oil anyway. Very cheap maintenence.