Royal Purple 11687 HPM Gear Lube 80W90 High Performance Synthetic Marine Gear Lubricant - 1 qt.

I have a 1994 GMC K2500, I had an ASE certified shop install a new crate 454 (7.4lt.) 22,000 miles ago, the rear axle has also been rebuilt- 4:10 gear ratio, the front axle has also been rebuilt- the NV4500 transmission is also new, I have used this gear lube in all areas that require GL 4-5 , it has preformed top notch, as with all Royal Purple products, they are a bit pricey, but so is a new truck- if you want the very best in all lubricants- Go with Royal Purple, this 80w-90 is a grade above the 75w-90 with the additives that make it favorable for marine use- Thanks Amazon and all those who take the time to review the products we need, and Thanks Royal Purple for the very best in lubricants that help make our vehicles last

Seems to work well. It stopped clunking hard when engaging the drive. Keeps the foot from getting as hot. You could tell the difference after a long run and feeling the foot after jumping in for a swim. Only one season of using, so no long term opinion. I would buy again. Seems sticky though like chainsaw chain oil. Hopefully that is a good thing. Time will tell.UPDATE: I have just changed the oil after about 35 hours of running. Looked like new oil. The magnetic plugs only had a slight gray tint of material stuck to them. I replaced with Royal Purple again and changed the rubber washers to the plugs. This is my new gear oil.

Good product, but not compatible with standard marine lower unit fill pump. Had to be transferred to a typical one quart oil bottle. It appears that the current illustration of this product shows it in a typical one quart oil bottle.

It royal purple nothing more to be said about that! I run a 2013 4 stroke 20hp Tohatsu outboard on my jon boat and i only run royal purple in the lower unit and royal purple hpm 30 in the main! Bet my motor last longer than yours its all in the oil folks!

My lower unit is wearing out so I put this stuff in there and got me though a month long camping/boating trip. Don't think it would have made it without the Royal Purple. I have Royal purple in everything on my F250. No problems

used this in my Merc outboard lower unit. Enough for two oil changes. Prob the best gear oil you can buy. Why save a few bucks, and take a chance on a huge rebuild price?

We own a Label manufacturing company. Our press operators scream for this stuff. It works great for reducing the heat and lubricating the gears of our presses. I would highly recommend this product!

Quality product. I've noticed working with Royal Purple products that its hard to wipe the oil film off parts and your hands..