Adding MOS2 in Volvo Penta5.7 engine, a good idea?

[Yannick]

Boat gaz engine;
-Volvo Penta 5.7 2008
~600hours
-are running fine.
-small leak on main rear seal
-Oil capacity ~5-6liters
-Running her with Mercruiser 25w40 non synthetic oil

what do you think adding a MOS2 can in that engine? Can this affect my seal/gasket?
I read a lot of good post on MOS2 but what to be sure on marine (GM block) engine.
thanks

 

[Donald]

The Mercruiser oil is a great oil. I would use Auto-Rx (for the seal) before I even considered LiguiMoly.

 

[Rolla07]

Id use something specific for fixing the rear main leak first like Donald said.

 

[ARCOgraphite]

Colloidal MoS2 is not formulated into any major motor oil for good reason.

 

[Trav]

I began using this product in the early 80's when 15w40 oil was the most inexpensive popular oil in Germany.
It seemed to help preventing camshaft wear well enough and was cheap enough which was important because i couldn't afford high quality oil in those days.

I believe it works as advertised but i today i have reservations, i am concerned about dropping out of suspension because my cars sit either all winter or all summer.
This concern apples to all solid type additives, MoS2, Boron Nitride, etc.

Todays engine oils are so good i have to wonder if any additive can improve them very much.
Esters reportedly help soften seals but rear main seal leaks are usually beyond anything in a bottle.
Personally i wouldn't bother with ARX, it didnt work very well in any engine i tried it on and its expensive. If you must try an additive you could try Lubeguards engine formula which contains esters and soluble moly.

If it were me i would use the oil as is and live with the slight leak.

 

[Johnny248]

I've been running LM Mos2 in my VP marine engine for a few years. Nothing negative to report. Its still just a SBC engine and it won't have any effect on your seals or anything like that.

 

[Donald]

The OP wants to fix the rear seal, thus I suggested Auto-Rx. A synthetic oil might also be good.

If you do not want to use Auto-Rx, go with Rotella T6.

 

[hattaresguy]

Waste of money, fix the seal if its bad enough.

 

[Yannick]

Nah its not so bad , I have 1-2 small drop(s) per ride. Main rear seal is a big job on a boat.

This is why I tried to fix it slowly by adding the best stuff available on the market. I added 1/3 of Kleenflo bottle in my engine last week end.

Planning to do my oil change in 3 week end with Mercruiser Oil. I will probably added Lubro Moly (oil leak seal), just half bottle. But adding MOS2 also will be a little much.

My original goal was to add Valvoline MaxLife , but no 20w50 available in Canada

 

[Trav]

It doesn't sound like the seal has been mechanically damaged, of course thats just a guess but mechanically damaged seals as a rule leak a lot more than 1 or 2 drops.
Some additives need time to work sometimes a long time if the engine is not in daily use.

Now you have already used one product i would skip using another right away. Seal swellers swell all seals in the engine not just the rear main seal, that scares me.
My first and only real experience with seal swellers was not a good one. I had a new motorcycle with hydraulic forks, after 2 years i decided to change the oil (overkill and OCD).

Make a long story short i bought a brand name oil from a motorcycle lube company and didn't think much about the words "contains seal swell" on the bottle. Within a few months i had leaking forks.
The seals were all soggy and had no rigidity.

I cleaned and re sealed the forks and used a no swell synthetic oil and never touched it again. 10 years later it was still bone dry.

No bash of any product or implying the newer generation of these products will cause the same thing, just sharing my own experience.

 

[Clevy]

Originally Posted By: ARCOgraphite
Colloidal MoS2 is not formulated into any major motor oil for good reason.

Well other than liqui-Moly's own 10w-40.
OP. Mos2 is great stuff. I use it in everything I own. As far as dropping out of suspension I've never seen it happen and I used it in my mustang which only sees summer duty.

 

[demarpaint]

I'll be the Devil's advocate and say I actually think the MoS2 might help stop that very small leak. In fact if it was my boat I'd give it a try. From my experience MoS2 fills small voids, and as long as the product is in use those voids will remain filled. I'd use that before any of the other products that were mentioned so far, or do what Trav said and live with it.

 

[hattaresguy]

you can try the snake oils but I have never had any luck with them, your either going to have to yank the motor and replace it or live with it.

Pulling a motor out of a boat like that is pretty simple, I'd have it out and back in on a Saturday.

Last winter I had to yank the twin disc out of my boat and for good measure while it was out I spent $100 on a Cummins rear main and did it. Knock on wood my white Cummins stays white, screw oil leaks!

 

[Yannick]

For your infos, I added KleenFlo no leak stuff (3/4 bottle) inside her, and after 5hours , no more leak ! Wow!

thanks oil technology !