The spec for my Honda 135 outboard gear case oil is: API STANDARD( GL-4/5) SAE 90 outboard motor gear oil.Does this mean that I can use GL-4? I have a lot of GL-4.
I have used Amsoil products for 15 years and love them. I'm sure the marine gear oil they have is great, but I have not had a chance to give it a real world test.
I have a 60HP Merc I will be trying it out in the summer though.
I'm positive it's a much better product than the Honda stuff that is a dino gear oil. I have seen some guys with commercial boats coming into our shop that have some pretty dark Honda gear lube coming out after some hours on it. I don't know how many hours they put on though.
I just use 75W90 Pennzoil Marine Gear Lube from Walmart @ $5.60 per quart.
It's just a 20 minute job to change lower unit lube.
It does the job, and is cheap. You can spend more, but you won't find any lube that does any better job of protecting your lower unit.
I work at a Honda marine dealer. Honda gear lube is a partial synthetic gear lube. So You might want to either use the honda gear lube or move up to a full syn gear lube. If you run a dino gear oil change it often or keep a close eye on it.
Some of the boats that come in beat the snot out of the Honda partial syn gear lube. They run it out too far.
