First of all... I have always used Merc OEM gear oil and will continue to. Is there really any difference between them? Merc has the SAE-90 spec and others usually are 80-90 or 85-90 and state for marine use. Does Merc have some "magic" additive that the others don't

thanks

been using 75-90 automotive synthetic GL5 gear lube for years and had no issues,

[QUOTE=PA.WOODCHUCK;4733613]First of all... I have always used Merc OEM gear oil and will continue to. Is there really any difference between them? Merc has the SAE-90 spec and others usually are 80-90 or 85-90 and state for marine use. Does Merc have some "magic" additive that the others don't

thanks[/QUOTE
Magic additive is "green sludge & $$$$$".

What drive are you putting it in? In one boat I put a high end gear oil in started having cone clutch slipping issues, that went away when I put merc oil back in. I believe the merc oil has a friction modifier in it. Also I believe there is no difference between the Sierra brand gear oil and the mercury.

Bravo 1 X in current boat

Walmart usually has it for 9 bucks a quart or so....

Its mineral base the Merc High performance gear oil and is a GL 4 spec. All the 75 w - 90 syns are GL 5 spec.

You can not use Merc HP gear oil in Volvo SX / DP and current drives with Nedox cone clutch. Some added info for the Volvo owners.

You can also use the "Quicksilver High Performance gear Lube". It’s the same blue/green stinky stuff as the "Mercury High Performance Gear Lube Plus", just a different bottle.

Sierra and Merc are not the same.
Quicksilver products are the exact same product as Merc with a different label and QS can be sold at non Merc dealer retail places.

Also available at Menards, if you have one by you. My local Walmart had 2 bottles last time, Menards had 20.