Volvo Penta DP290 OD lube

[KMC]

My boat is a 1995 Cobalt w/7.4 BBC and VP DP290 outdrive.
When looking in the manual, this out drive calls for Gl-5 spec full synthetic marine lube. Why do they specify full syn. 75/80wt. marine lube for this dual prop out drive?
Talking to boat mechanics, and on boat forums, I got the same answer, "because there is a cone type clutch in this Out Drive unit".
Agreed, there is a cone clutch in this unit. My question is, why can't you use a bottle of limited slip additive mixed with GL-5 mineral based oil and have the same protection as the "full syn marine lube" ?

Am I missing something between the two types of lube, other that the fact full syn is 3 times more expensive? Both of the oils are GL-5 spec. The only thing I see different in the full syn, is that the limited slip additive is already in the oil.

I check/change the lower unit oil yearly on my bass rig. Making sure there is no moisture getting inside. This is the first year with this boat and my first service interval. Before I do anything, I decided to research this area.

I'd like some concrete answers on this from oil experts, not just speculative answers from average Joes that change their out drive oil in their driveway. I don't need answers stating, "use what is recommended by the manufacturer", unless you can tell me that the mineral based 75/90wt. oil w/LS additive will not work in this application and why it won't work. Thanks guys.

 

[KMC]

WOW! 40 views and no one has a reply? I hope I didn't come off as a hard butt in my first post.When you come to the oil place to ask technical questions about oil, you want good answers, not guesses. I guess. Ok experts let me know what you think about the LS additive in the Penta Out Drive.

 

[cchase]

FWIW, I don't know on the DP units, but on the SX units they spec Volvo gear lube or, if that is not available, M1 75w90 gear lube.

 

[Johnny]

To add to the PM you sent me and that I replied to, the marine gear oil has extra emulsifiers in it to help with water contamination in case water gets in there.

 

[rmattingley]

I also have a duoprop drive and I run the volvo branded stuff in mine. Ive had amsoil in it, but decided that saving $10 once or twice a year was not worth it on a 5 to 10 thousand drive.

 

[ac_tc]

Just because an oil is syntethic doesent mean that
it has ls additive in it. Your drive was from factory filled
with a mineral GL5 oil and will function on any brand and make
of GL5,nnW-90 oil. A syn will probably last longer but the oci for a drive makes it almost impossible to wear the oil.
I would not add ls additives or use oil with these iném.
Dont mess with the cone clutch! (it has been around since the old 100 drives around 1960 or so and proven reliablie, but
never required ls add´s)

 

[lars11]

Interesting question. Volovo recommends volvo own 75w90 gl5 AND Mobil1 75w90 synthetic...
Why so picky? Are the volvo and mobil oild extra good in some sense? Or can you use any 75w90 GL5 full synth?
I always used volvos own since the mobil 1 is just as expensive.