Should I be worried?

[kilou]

Hi,

I recently tried an MoS2 oil additive in my manual gearbox. I used Liqui-Moly gearbox oil additive and mixed it with my current almost new 75W80 GL5 oil. I've renewed my clutch now and had to drain the gearbox oil (+additive) but I wanted to reuse it since it was only 1000km old. The gearoil is black due to the MoS2 additive. When I poured the mix back in I noticed that there was some foam building up in the funnel just by pouring some of the used oil in

I then tried with some fresh oil and there was no foam in the funnel!!!!

I wonder if this additive causes the gearoil to produce foam easily! This wouldn't be a good thing obviously. However I used only one tube of MoS2 (20g) in 3.4liter of oil and this is less than what is recommended (1 tube for 1-2 liter normally). This additive is well know in Germany and Liqui-Moly is known to be a "serious" brand... Liqui-Moly states that this additive can be used with any type (dino, semi or full synthetic) gearoils and it is designed for synchronized manual transmission.

Do you think I should immediately drain out this stuff or is it OK to leave it in? I can't say the additive improved anything but it didn't degrade the gearshift so I'd like to leave it in until the next oil change because the oil itself is pretty expensive. The problem is really not about effectivness of the additive but about its safety.

What would you recommend? Does foam produce in a funnel when pouring in mean that the gearoil + additive will produce lots of foam in the gearbox as well???

Thanks

 

[kilou]

EDIT: By foam I mean air bubbles on the surface

 

[TimVipond]

It would be interesting to see what would happen if you put the gear oil in a blender. Try different speeds. Then try the gear oil plus Liquid Moly. Then buy your wife a new blender! Foam stability is a gear lube test, i.e. Foam Stability (ASTM D-892). I'd say if you notice more foam with the additive than without, it is a bad thing. This is why I try to buy the lubricants with better typical properties than buy cheap and add additives.

 

[Trav]

Liqui-Moly is a respected brand and their products go through genuine testing by TUV.The gearbox additive is a very small amount and will not cause additional "foaming".By additional i mean if you had Lucas(see Bobs experiment)in there it would foam and the moly would have neither positive or negative effects.what you are seeing are probably just normal air bubbles.I would continue using the oil.

 

[mechtech2]

I'm thinking of the reduced friction of the synchros and cones, making for poor shifting, because of the moly.
Moly is not normally advised for manual trannys.
If you think it's shifting fine, the moly's not doing anything, and it will shift better anyway with the proper sauce in there.

 

[kilou]

mechtech2, many people have advised against using moly or any kind of friction reducer in a synchronized manual transmission and this definitely makes sense. However I contacted Liqui Moly to ask them why and how their moly additive could improve shifting with synchros as those requires friction to work effectively. They were very prompt in their reply and explained that moly doesn't improve the way synchros work but it makes the gears more slippery. They insist on the dosing: no more than 20g for 1-2 liter of gearoil! If this is respected, the small amount of moly doesn't affect the synchros at all while it help protect the bearings and gears. This additive is mainly designed for improved protection and only in second hand for improved shifting. The improve shifting is mainly possible for old gearboxes that already have some synchros problems. When you have synchro problem, the gears grinds sometimes because they are not well synchronized. This is where moly helps because grinding gear teeth will get easily in mesh with moly because they can slide rather than grind. Of course a working synchro is much better.... At last moly reduces the noises which makes the transmission a bit smoother. These replies did quite make sense to me. Basically it is all a matter of dosing: too much moly and the synchro won't work well, but if you put a little moly in there the synchro are not affected while the beneficial properties of moly can work on bearings and gears efficiently.

Honestly I can't really tell if there is any difference with this additive in my tranny but for sure the tranny doesn't shift worse than before! I don't think it was of any help in my case but I just wanted to try. However I'm a bit scared by those air bubbles that seem to be due to the moly additive. I also think that as Liqui Moly is a reputable brand and that this additive has been tested and certified by TüV Germany, it should be OK to leave it in the gearbox.....but those air bubbles are definitely weird.

Trav, I saw the Lucas additive experiment and it's quite scary. This is mainly why I'm wondering about the "safety" of this Liqui Moly additive. You say that wih Lucas it would foam and moly would have neither positive or negative effects. I'd say that if it foams, no matter if moly is in there or not, it will have negative effects! Foaming is really not good in any circumstances and the fact that I see air bubbles forming just by pouring the oil+additive mix in a funnel makes me fear that a lot of foam can be produced when the mix is in the box at high speed. In the fresh oil (without the additive), air bubbles immediately disappear but with this additive the air bubbles form and slowly go to the surface.....and stay there for a while.

I'll probably try to put this in a "mixer" if I can find one to trash afterwards so that I'll know what can possibly happen in my gearbox.

Maybe this additive is just "incompatible" with my gearoil. This gearoil is a very specific one (Kroon-oil SP1051). It's a 75W80 GL5 safe for brass synchro and with a "specific" additive pack (non borate additives). Probably that Liqui Moly cannot test the compatibility of their additive with every oil. As an example I read that it is not recommended to mix a non borate additived gearoil with another gearoil with same weight and spec. Maybe non borate additives (I don't know what that means though) do not like MoS2 ??????