Gear Lube question ?

[bigdog]

I have 90hp Johnson outboard 2 stroke.

Silly question....
The gear lube recommneded by Johnson/Envinrude for the lower unit is 85w x90. Would it matter if I refill using a 80wx90 lube, is there that much difference in viscosity?

Also, can I buy auto gear lube same viscosity, at auto parts store or WalMart? The type lube they sell is for automotive though....
Is marine gear lube made differently?

Interestingly, WalMart sells Quicksilver brand gear lube 85wx90, but the label specifically states, for outboards under 75hp ? WT* !
You telling me that there's different grades of gear lube depending on horsepower rating?

When I owned my Mercruiser I/O, I just used normal auto 85wx90 for years without problems.

Thanks for your feedback !

[DesertDweller]

Out of curiosity I looked at the gear case lube for my Yamaha and it's 80w90. Can't see a whole lot of difference between 80w90 and 85w90.

You are right on the Quicksilver/Mercury stuff the "high performance" stuff is designated for 75 horsepower and above. It's my understanding that product is very well thought of because it is very good at protecting the gear case if water enters. That's the biggest difference between the automotive stuff and the marine stuff. If it were me I would use the marine stuff and specifically the high performance stuff in the absence of using the factory stuff.

[JasonG]

I would get the exact type of gear lube suggested by the factory. Your lower unit is not something you want to second guess.

I own mercs and use merc lower gear case fluid. I would not think of any other brand even if it was free because it is what the factory suggests.

[Happy Gourmand]

I would get the exact type of gear lube suggested by the factory. Your lower unit is not something you want to second guess.

I own mercs and use merc lower gear case fluid. I would not think of any other brand even if it was free because it is what the factory suggests.

You can put any kind of gear lube that you want in your lower unit. The big question is why would you want to put in anything other than what the factory recommends? A lot of planning and engineering goes into recommending a certain viscosity oil that will keep everything slippery. If you think you know more than the engine manufacturer about their engine, then go for it! :)

[camp guy]

JasonG and Happy Gourmand both hit the nail on the head, each in their own way, but, nevertheless, their point is spot on - follow the manufacturer's recommendation (they are the pros).

[Dave R]

Oil thins when it gets hot and thickens when it gets cold. You want it to stay thick enough to be effective when hot, but you also want it to be thin enough to flow when it's cold.

The #1 thing to look for is the API service rating, (such as "API GL-5"). Once you are sure the oil meets or exceeds that requirement, hot viscosity is the next thing to look at and that's the second of the two numbers (90 in your case). The last thing to look for is the cold weather viscosity rating which has a "W" suffix. You need to make sure the lower unit's required cold viscosity is greater than or equal to the oil's rated cold viscosity. Thus, 80W-90 is a perfectly acceptable oil to use in a lower unit that requires 85W-90. It will just work a little better in cold weather.