Gear oil alternatives?

GMTK

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2004 4.3 GXI-E with a SX-M outdrive. Ordering parts for my annual servicing and the gear oil - OEM Volvo 75w-90 is $20 a quart. Wowsers. If anyone has a site where it is cheaper or a suitable alternative, please let me know.
 

Scott Danforth

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Many use Amsoil Synthertic Marine gear lube. About $9 a quart
 

Bondo

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Ayuh,..... I've been runnin' Mobil 1, 75W-90 in all my drives for years, 'n years,......
 

Lubak572

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Ayuh,..... I've been runnin' Mobil 1, 75W-90 in all my drives for years, 'n years,......

Well I was running that, but I have heard people (25 year marine tech) say not to as it will build up pressure and blow out seals. I have water in 1 of my drives so i will be re-sealing both. Not sure what to use. Guy above claims the car gear oil is designed for vented rear axles which boats don't have. I don't know if i should switch to amsoil or not??
 

bruceb58

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I used to use Mobil1 75w-90 until you can't ever find it without the friction modifiers. I now only use the Volvo gear oil and I buy it on iBoats.

For the small amount of gear oil you are actually using, we aren't talking about a whole lot of money here. Probably not the best area to try to save a couple dollars.
 
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Bondo

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Guy above claims the car gear oil is designed for vented rear axles which boats don't have.

Ayuh,..... That Guy, is talkin' out his butt,......

The differences 'tween automotive gear oil, 'n marine gear oil is the pretty colored dye they put in the marine oil,.....

That's why We have oil "Spec"s,.....
 

GeorgeDes

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You can order the Mobil 1 without the LS additive through Amazon. Difficult to find this in the automotive stores as most Mobil 1 they carry is with the LS additive.
 

jimmbo

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Volvo is very adamant about the oil being a Synthetic GL-5 oil.
 

jimmbo

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Ayuh,..... That Guy, is talkin' out his butt,......

The differences 'tween automotive gear oil, 'n marine gear oil is the pretty colored dye they put in the marine oil,.....

That's why We have oil "Spec"s,.....

I believe it is a little more than just a different coloured dye. The gears in an I/O are very small compared to the gears in a car/truck, but they have to handle the same same power all the same, so perhaps the additive packages are a little different.
I know my uncle used to listen to his 'expert' friend who told him that the oils were the same. Every summer after he changed the oil, using automotive gear oil, the upper gearcase would blow. He would get it rebuilt, and it would survive the season. I convinced him to use OMC Hi-Vis in the fall oil change, He never lost another gearcase. Coincidence? Maybe, maybe not
 

harringtondav

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I use NEO RHD 75w90 syn GL5 & 6 rated in my Alpha II. There is no relief here for your $20/qt cost. But it's cheap insurance against the cost of a gear failure holocaust. After 22 yrs I can still see traces of the cutter marks in the contact pattern of my gears.

And I'm with Bondo on the pressure story. Merc drive sealing is designed to use case pressures to force trace amounts of lube into the water, vs allowing water in. I'd guess Volvo is the same. "Blown out seals" sounds like a tall tale designed to sell Merc's lube. The check valve in the reservoir cap allows air to replenish when things cool down. So I don't get too excited if my reservoir drops a bit over a season. I know the drive is water free. When the level drops more than 1" in a season, I know I'm getting close to a reseal job.
 

jimmbo

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Many times there is water in the case and the oil level indicator is fine level wise. The gearcase can be full of water and the indicator will show nice fresh uncontaminated oil, as it has no means of mixing with the water and being oil will always remain at the top
 

QBhoy

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It’s all about the GL-5 rating. Use whichever 75-90 80-90 you like, but the gl-5 is a must.
 
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