Lower Unit Oil vs 80/90 Gear Oil

[gunflint]

What's the differences between them? Anyone know? Thanks.

[castindad]

my understanding is 80 90 is lower unit grease castindad

[BobT]

That's a good question. I have asked this of a couple marine mechanics and their opinion was that it's the same thing. But then, that was their opinion and they aren't design engineers.

Consider this. The lower unit runs under considerably less hostile conditions than the rear-end in your car. It has a much better heat sink, a lake, for dissipating the heat caused by the gears although they may be turning at higher rpm, I'm not sure. This could promote more potential for foaming I suppose.

I'm interested in hearing some sound thoughts about this.

Bob