I currently have Merc HP gear lube in my XZ drives. I'm switching to Amsoil Marine 75-80/90. Can I just drain the old lube or do I need to flush it somehow before putting in the new Amsoil?

I can't believe it, I was just quoted $76.00 for a case of Amsoil Marine Gear Lube! Kinda makes me wonder... does this sound right? Seems way too cheap.

Sounds about right.

I pay $72.00 for a case of six quarts of Royal Purple as a resale dealer.

Anyone? Simple drain or do I need to flush? If I need to flush how do I do it?

If your old gear lube was not to bad I would just refill with new and be done with it.

The oil is good, just doing the annual maintenance and wanted to make sure the two lubes were compatible. I don't want to have sludge or something develop.

If you didnt need to flush the old oil, theres no need to flush when going to amsoil synthetics. It will also mix with mineral oil. Im a 15 yr dealer, your drive will be very happy!!!

Thank you for a definitive answer! My local dealers didn't seem to know much about marine applications. Looking forward to trying it out as soon as I get my delivery.

I also use Amsoil products.

Do you guys think their Marine gear oil is better then the Merc HP Syn?

I was told the Syn Merc stuff is the best.

Mercs oil didnt even make the top 5 from independent testing.

My testing was on #3 speedmasters with all large shafts running 1100+hp. With the Merc oil we would burn up bearings and gears under 50 hrs. Changed to Amsoil and NEVER hurt a bearing again 150+ hrs at very high input shaft speeds. 1-1 gear ratio turning them 5700-6000 for up to 25 miles. The merc oil would puke out the vents @ 4-5 miles because of the heat.. Im sure everyone has a opinion but I run amsoil in everything I own, with great results!! The drives are still around