Best lower unit lube

[Reel crabby]

I’m pretty sure full synthetic lube for lower unit is best. This is why. I had an 80 ton crane (125,000 lbs) it had planetary gear final drives at each wheel. We put synthetic gear lube in one side and conventional gear lube in the other. After a road trip we checked temps with infrared heat sensor. Are you ready for this? The conventional lube side was 300 degrees f. The synthetic lube side was 200 degrees f. No combustion going on there! It was purely a result of reduced friction from greater film strength according to Amzoil. I use Royal Purple max gear in my f250 lower units because it’s gl4-gl5 and states it’s safe for use on brass, bronze and copper.

 

[robert graham]

Probably/maybe so on the synthetic lubricants….but for outboard lower unit gearboxes I’ve never had any problems with the Marine 80-90 Gear Lube in my motors…..possibly the biggest problem with outboard lower unit lubes is water intrusion due to leaking seals….especially salt water….

 

[JimS123]

Buy regular Mercury Marine lower unit lube. Its the best on the market and it will not void your warranty.

 

[Scott Danforth]

I’m pretty sure full synthetic lube for lower unit is best. This is why. I had an 80 ton crane (125,000 lbs) it had planetary gear final drives at each wheel. We put synthetic gear lube in one side and conventional gear lube in the other. After a road trip we checked temps with infrared heat sensor. Are you ready for this? The conventional lube side was 300 degrees f. The synthetic lube side was 200 degrees f. No combustion going on there! It was purely a result of reduced friction from greater film strength according to Amzoil. I use Royal Purple max gear in my f250 lower units because it’s gl4-gl5 and states it’s safe for use on brass, bronze and copper.

the gear lube recommended in the factory manual is the best for your motor. since you dont say what lower unit you have, I suggest you look up the factory manual and go from there.

not sure what brand of crane you are referring to, however your overall weight is extremely light for an 80 ton crane that has any length of stick to it.

 

[Reel crabby]

the gear lube recommended in the factory manual is the best for your motor. since you dont say what lower unit you have, I suggest you look up the factory manual and go from there.

not sure what brand of crane you are referring to, however your overall weight is extremely light for an 80 ton crane that has any length of stick to it.

The crane was a Krupp 70 GMT with 188 ft of boom and jib. I’m certainly not implying that there are not other good lubes. I have a 29 Blackfin Combi with twin Yami 250s. It’s a heavy boat with 320 gal of fuel. I push her hard fishing 75 miles offshore. I can’t believe the lower units can survive that much punishment. I’ve had good luck with RP Maxgear but again I’m sure there other great lubes too.

 

[Reel crabby]

Probably/maybe so on the synthetic lubricants….but for outboard lower unit gearboxes I’ve never had any problems with the Marine 80-90 Gear Lube in my motors…..possibly the biggest problem with outboard lower unit lubes is water intrusion due to leaking seals….especially salt water….

I agree! No argument here!

 

[Texasmark]

Mercury Premium LU lube is in WW, in the sporting goods dept. They don't bother to mention if it's synthetic but its credentials (otherwise) are on the bottle. Comes in a quart with a tube and adapter to fit the threads in your drain hole.......pump also supplied. Can't get any easier than that...all at a reasonable price.