Is It Safe.-

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Is it safe to mix 50/50 % of 2 different gear brands oils leftovers, both are SAE 80-90 API GL5 car transmission gear oils, Could there be any form of lubrication incompatibility for gear case to wear faster? or no issue at all being same SAE and API ?

Happy Boating
 

IamMe

Cadet
Joined
May 30, 2016
Messages
25
As long as both fluids are clean and free from contamination there should be no harm providing the are to the same standard as you say. In all Honestly most of the oils come from the same place just like gasoline. The final retailer Shell or Marathon or who ever adds an additive or two to make it there blend.
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
It is not advisable to use automotive gear oil in a marine gearcase. Due to it has no additives for emulsifying water and aeration as a transmission/rear end on auto/truck is vented.
 

Sea Rider

Supreme Mariner
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Sep 20, 2008
Messages
12,345
Thanks, but been using automotive gear oil SAE 80-90/API GL5 for the last 20 years is many OB's brands with no gear failure whatsoever. Don't know why this theme gets so picky with respect that needs to be certified marine gear oil. We have a whole country using automotive fixed 90 grade or 80/90 multigrade for decades. Those fancy "marine" grade gear oils which the label doesn't specify being as such are not available down here. Tohatsu being a reputed outboard brand, specifies in their Owner's Manuals to use any good quality multigrade 80-90 gear oil that meets or exceeds API/GL5 specs.

Happy Boating
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
This a recurring old theme with boaters that swears by them along detractors as well. Just posted my personal boating experience with good quality automotive gear oils. I'm not playing with fire nor hornets as well.

If you boat with new OB's that counts with fresh and flexible oil seals & o'rings don't need that marine stuff as won't see water intrussion any time soon, if boating with very old ones which you like using and buying as well as opposed to new ones, you definitely should. You should change as a preventive maintenence all lower leg seals from time to time to avoid failures, ensures no water intrussion which most boaters are definitely not doing due to a cost issue, time, what the heck issue, who knows.

Oil seals can fail any time due to : OB being very old and consequently oil seals too, OB seats for long time/year periods in heated closed environments or exposed to excessive & direct sun punishment while lower legs remains fully trimmed up for long time. in these cases, oil seals becomes dry and hardens, won't seal to perfection on prop shaft as a fresh one will. Water intrussion is fully guaranteed in the short run.

Why don't we start a gear oil poll to see how many Iboats users uses marine gear oils and which ones automotive gear oils, Just state OB manufacturing date as a reference.

Happy Boating
 
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hardwater fisherman

Lieutenant Commander
Joined
Mar 19, 2010
Messages
1,725
I have used both marine grade gear oil and gear oil that I use in my truck. My opinion is that if you have a gearcase that does not let in water than there should not be much difference. I have found the marine grade gear oil mixes with water to make a milky color. Where as the standard gear oil will separate from the water. This is just my experience. I have all older OMC motors with two piece gearcases so I pay the little bit extra for marine grade. But if it was not easy to find than I would not worry about it. Two of my manuals say to use OMC Sea-lube premium blend gearcase lube. I am not sure if that is still for sale. I use castrol marine grade.
 
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