Molybdenum Disulfide - Unitended Consiquences

[WhatAmIDoing]

Molybdenum disulfide, also known as MoS2, is one of the best solid lubricants around with a friction coefficient of less than 0.1. It is also the oil additive that cemented Liqui Moly existence as a premium engine oil manufacturer. Molybdenum disulfide oil additives claim to increase fuel economy, improve cold starts, and protect your engine from a complete loss in oil pressure. MoS2 accomplishes this by sticking to the metal surfaces in your car, forming a film of MoS2, which greatly reduces friction. MoS2 does work, and is perhaps one of the only oil additives that actually does what it claims. This thread isn't meant to discuss Molybdenum disulfide's legitimacy, but more to examine potential unintended consequences.

1) Does anyone use MoS2 regularly in their vehicles?
2) Since MoS2 sticks easily to metal surfaces, is it possible it could block up small engine ports, like for the PCV system?
3) Could MoS2 aggravate existing oil leaks? Or is it more likely that it would stop leaks by forming a film against seals?
4) Could it cause leaky seals to pop out by forming a low friction surface around and on both sides of seals?
5) Is there a point to adding MoS2 to synthetic oils like Mobil1, or do synthetics do a good enough job that there's no point?
6) Would MoS2 not behave well when added to high detergent oils, as in do you think the detergents would prevent a film of MoS2 from forming?
7) Do you think Molybdenum disulfide additives are just a gimmick and/or this is a pointless thread?

I ran Liqui Moly MoS2 additive in an old Suburu Forester since it was at 200k miles. MoS2 did improve fuel economy, power, and cold starts. By 280k, the engine was leaking oil like a sieve. Oil was leaking past every seal in the engine to the tune of >2 quarts per day. I have no idea whether MoS2 contributed to the complete loss of seal integrity, or if those seals would have been done by 280k miles regardless. I have always wondered though.

I want to start using MoS2 in my Volvo to improve cold starts and fuel economy, but these thoughts have always haunted the back of my mind.

[ZionXIX]

I use the LiquiMoly 5w40 oil. I have noticed no ill effects in a 200,000mi engine.

[misha]

I used Liqui Moly Mos2 10w-40 oil in my car for two years without problems(Lubro Moly for U.S market).
Why adding MoS2 additive separatelly in oil when you can buy oil which allready have it and properly balanced?

I didn't noticed any improvements,but didn't had any side effects.

[WhatAmIDoing]

I used Liqui Moly Mos2 10w-40 oil in my car for two years without problems(Lubro Moly for U.S market).
Why adding MoS2 additive separatelly in oil when you can buy oil which allready have it and properly balanced?

I didn't noticed any improvements,but didn't had any side effects.

Because 6 quarts of Mobil1 and MoS2 additive is way cheaper than 6 quarts of Liqui Moly.

[mrbrian200]

Regarding the Subaru, it might be worth the effort to research whether multiple major oil leaks are a known issue on higher mileage Subarus. The probable source able to give a more definitive answer might be a dealer SM.
A quick google search seems to point to a strong possibility that this is the case on models before ~2007 (common leaks from head gasket, PCV cover, front crank seal, oil pressure sensor)

[WhatAmIDoing]

The guy I sold it to said the crankshaft seal was all the way out. That was why I proposed the question of whether MoS2 could cause leaky seals to be easily pushed out. As for whether that seems to be expected on a Subaru, my research seemed to be half old Suburus had no oil leak problems at 300k miles, and the other half had more oil under them than in them. I would wager that oil leaks are a problem on high mileage Suburus, but wonder if 80k miles of MoS2 may have accelerated its demise?

[misha]

Because 6 quarts of Mobil1 and MoS2 additive is way cheaper than 6 quarts of Liqui Moly.

Not over here in EU.The price is the same like Mobil,Total or Castrol or Liqui Moly super leichlauf 10w-40.

I got it from official dealer....so it might be because of that.

[jimmy57]

The Moly is not that slick. It's purpose is to form a film that makes any metal to metal contact less likely. If car is parked for long periods it keeps oil film on bearing journals longer.
When an engine gets more miles and has more ring leakage it gets more crankcase pressure. The seal at the same time gets hard and shrinks a bit. Recipe for the pressure to push out the seal.

[mrbrian200]

I concur - an old prune subject to increased internal pressure and heat cycling are probably the factors responsible for the blow out. Not the metamucil.

[andrewmoore70]

Please read if you are truly interested in unintended consequences of MoS2... I have not tried MoS2 (molybdenum disulfide / molybdenum disulphide) additives in a volvo yet, but I have some knowledge of undesirable effects and potential effects in another car.

Firstly, there are many comments on the (highly) beneficial properties of MoS2 floating around on the internet, and most of them are very indiscriminate as to the exact mode of use: yes, MoS2 can offer greater wear protection to joints and bearings - particularly sliding bearings such as crank bearings and CV joints (e.g. drive-shafts directly to wheels) - and can even, for a time, prevent catastrophic bearing damage if the oil or grease runs dry. Burnishing MoS2 onto the surface of relatively large sliding bearings of the cups of tapered roller bearings (i.e. forcing the MoS2 powder into tiny irregularities in the metal surface by rubbing with a tool made of slightly softer metal) is a process that some professional engine builders and mechanics apply. Furthermore, it has been said that the military added MoS2 to engine oil in a variety of vehicles to protect them against oil loss during combat.

Secondly, one must understand that these applications are not directly relevant to routine oil changes in modern cars running on modern (partly synthetic, or fully synthetic) oils that, furthermore, contain a variety of additives that the oil in military tank engines from decades ago didn't. MoS2 powder will not dissolve in oil; at most, it forms a fairly coarse suspension - much coarser than you would imagine from the tiny particle size (more on that later). There is practically no way to achieve a fine and lasting suspension of MoS2 in the context of (modern) engine oil, and here is where the problem gets even worse if you try to do this yourself with MoS2 powder - even if you've gone to the trouble of working out exactly which microparticle size you need and ordered it from a reputable supplier! I know, because to my shame - I'm a chemist and biochemist - I have made this mistake, but to be honest, I could not predict several parts of it, and so I am writing this to prevent others from finding out via experimentation.

I will work backwards in time from a catastrophic turbo failure in my 2014 VW 2.0 TDI engine (not a Volvo, of course, but I reckon that turbos are quite similar between modern diesel cars) that had been serviced in exemplary fashion (partly by me), using good quality longlife oil and filters etc. etc. For environmental reasons, I wanted to reduce diesel consumption to a minimum, and I had read in many online forums that MoS2 added to engine oil produced quite remarkable results in that respect. Yesterday the mechanic who replaced the whole turbo unit - because of a sheared turbine shaft -, at great financial cost, showed me the oil filter and pictures of the oil filter holder from my car: the base of the filter inside and out- , and the filter holder, were caked with a dark grey sludge. Though there was no sludge to be found in the oil lines to and from the turbo, the mechanic reckoned that the MoS2 had blocked the small appertures to the oil circulation within the turbo shaft, hence leading to bearing damage followed by shaft failure. That happened 10,000 km after my first oil change with added MoS2. Ok, nobody can prove this now, because nobody split the damaged turbo to inspects its innards, and I was not able to take the old turbo unit with me, because the deal was "send back to manufacturer in return for the new unit". Still, the mechanic's logic makes sens in combination with other observations.

So here is what I conclude from MY experience: MoS2, even in the fine particle size recommended for use in lubricating oils, will not remain in suspension long enough to coat all metal components in the engine; rather it will clump together relatively quickly and deposit in a number of places where it will not help, but probably hinder, the correct functioning of the oil circulation in the engine. I thought that the tiny amount of MoS2 that I had added (around 0.5% mass for mass of oil) would surely circulate nicely (particle size smaller than oil filter pores) and coat all important engine parts quickly, thus taking it out of the circulating oil, because I drove the car immediately after the oil change. Not so: despite the fact that I whipped it up into a very good suspension before pouring, instead it clumped together to form a thick sludge in various places (probably much is still sitting at the bottom of the oil sump pan). Why did it do this, despite what one can read on the internet, e.g. "...rapidly forms a film that covers metal surfaces..."? Firstly, MoS2 probably has a tendency to do this in any oil, because it consists of microscopic sheets that behave a little like playing cards: spread plastic-coated playing cards onto a table, tip a little liquid onto them, and they will stick together and be very hard to separate or order into a stack. Secondly, I have since read that modern engine oils contain additives that might react with MoS2 to create larger particles: calcium and zinc compounds are mentioned. Not only would this favour the production of MoS2 sludge, but it would remove from the oil the very additives that manufactures put into it to protect your engine!

Finally: the most important fact is a chemical one (shame on me, again): there is, indeed, molybdenum in certain modern engine oils, but it is NOT MoS2; rather it is an oil-soluble form of molybdenum - essentially an organic molybdenum compound. This has been tested for adverse effects by the manufacturers and is already present in the oil from the factory. Some oil manufacturers even sell a molybdenum additive that one can add to oil oneself, but I really can't comment on that.

Finally finally: I will never put MoS2 in my engine oil again. It might have provided some minor benefits, but the disadvantages obviously outweighed the advantages. Even if my turbo failure was not a direct result of the MoS2, the thick sludge that MoS2 formed in my engine oil is clearly a very bad side-effect...