This is for a outboard marine engine for the lower unit. I went to the D&R sports place and this was the only "marine gear lube" they had. It says it's safe for all outboard marine engine lower units without electric shift.

So I bought it but my manual which I learned after the fact says it needs SAE 90 hypoid oil. I don't what the heck that is and can't seem to find it anywhere? Any ideas? Is this 80W-90 oil safe to use for this purpose?

 

80W-90 oil is as thin as an 80W oil when cold, and as thick as a 90W oil when hot.

A 90W oil is 90W hot or cold.

So an 80W-90 will be a little bit thinner than a 90W when cold, but will be essentially the same when hot.

90W hypoid marine gear oil is still available. CRC makes it and I think that it is available at Advance Auto Parts. If not there, it is available on-line at:

StarboardSupply.com - - Inexpensive boat/ship parts

shipstore.com -Part of - ShipStore.com ™

 

Gear oil viscosity is defined in SAE J306, which has been revised.

SAE J306 Specifications - The Lubrizol Corporation

SAE 90 gear oil is about the same viscosity as SAE 40 motor oil at 100C (212F). Adding the 80W to it just means that it has been tested to barely flow at -26C.

Note that 90W does not exist, even if Star Brite distributing incorrectly labels its product as such. Straight 80W, which I have never seen, is about as thin as SAE 20 motor oil at 100C.

As far as the word "hypoid", that term has been replaced by API specification GL-5.

So, you can buy a special marine product, which may or may not have better corrosion protection, or 80W-90 GL-5 automotive gear oil, which costs only about $4 a quart.

Jim

 

Star Brite 90W marine hypoid gear oil (correctly labeled or not, special or not) is about $7/qt.

So he can buy something that is probably OK for $4, or exactly what the manufacturer recommends for $7.

BTW - Red Line and Royal Purple both make full syn 90W gear oil for about $12/qt. and should be available readily at his local auto parts store.