View Full Version : Transmission fluid type

04-19-2012, 04:45 PM
Has anyone replaced their transmission fluid with a synthetic such as Amsoil or Royal Purple? I'm getting ready to change mine and wanted to go to a better fluid. I assume these transmissions will take that kind of fluid with no problems since both brands are compatible with Mercon/Dextron and they mix with traditional fluid. Boat is a DD '01 Outback.

04-19-2012, 08:19 PM
I have not changed to a better fluid in any boat that I have owned, so I can't be of any help there. I can tell you that a DD transmission does not experience a great deal of stress and that there probably is no benefit, especially if the cost is a lot more. With the water cooling, your tranny doesn't really get hot, there is only one "speed", and most people don't jam forward/reverse constantly. Many of the reasons car tranny fluid breaks down more rapidly than boats. Just my opinion. With the outragous price of fluids, I probably won't be going with expensive fluid

Cigars n scotch
04-19-2012, 08:23 PM
Great advice maxpower, couldn't of said it better myself. Save yourself the money and just go with a standard or what your manual says. I put sae30 pennzoil in my vdrive.

04-19-2012, 09:16 PM
I have replaced the fluid in my OB. Suck out the old, pour in the new. I used conventional, but that was because when I did it, the store I went to did not stock synthetic ATF and I did not want to make the trip across town to pick it up. If I recall, it only hold 2-3 quarts, would have to refer back to the owners manual to be certain.

But like mentioned, probably not significantly different than conventional oil in this application, except for price, especially if you follow the maintaince guidline.

04-22-2012, 03:23 PM
Prolly right. I guess I should use the extra cost for gas.


04-22-2012, 08:39 PM
so if the stress on the transmission is so minimal then why do we have to change it once a year when cars can go years on the same fluid

04-23-2012, 02:42 PM
That is a good question David. I would guess that it probably has something to do with the possibilty of getting water in it? I changed mine when I got the boat, and then after the first year (about 100 hours) and the stuff looked like brand new.

Also, you V-drive guys, don't forget your boats have a transmission AND a V-drive unit. The transmission takes trans. fluid, and the V-drive probably takes motor oil (usually 30 weight). Don't forget to check both, and make sure not to swap fluids, it would probably be a disaster.

04-23-2012, 09:48 PM
It doesn't cost the manufacturer anything to print out a manual that states X,Y, or Z for fluid changes. At some point, the engineers thought it need to be changed that often. Most likely due to the marine environment and basing it on the lowest common denominator user. Your car owner's manual may still state to change oil/filter every 3,000-3500 miles, but probably isn't needed there either. Tranny capacity is roughly 2-4 times as much as the boat.

You probably can't ever hurt your boat by using the manual guidlines for maintenance.