MMO potentially causes gasket/seal leak, and do I use additive?

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Sep 11, 2020
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Wisconsin
Hey, all. About 6 months ago, I bought an 09 Pontiac G6 V6 3.5 base sedan w/ about 139k on it. Not a drop of fluid leaking, garage-kept, one owner yada yada - clean as hell and in excellent condition. I changed the oil about 3 months ago (Supertech synthetic 5W30, Fram filter), no sweat, no issues. Well, I decided it was due again now that it has 145k+ on it. I heard about Marvel Mystery oil, and decided to check it out. Since I was/am going to change the oil in about 500 miles, I figured I'd throw some in the oil, and burn off any crud before my next oil change. I put about 12 ounces in the crankcase. Well... since then, I have developed an oil leak from what I believe is the front crankshaft seal (I assume this because there is wetness on the passenger side frame rail right below the front crankshaft area both directly underneath the belts/crankshaft and accumulating on the frame rail underneath the same area). There is maybe 2 to 5 drops of oil after every other time I drive (I drive for about 45 min at a tie), and never when sitting overnight. I know it is anecdotal, but... did the MMO clean the crud from around the seal, thus exposing the leak, and/or did the oil thin sufficiently to seep out of this exposed leak?

Also... I bought Valvoline HM synthetic blend Maxlife for the impending oil change -it has seal revitalizer, I guess... should that suffice as a band-aid or should I add a bottle of the Blue Devil Stop Leak as well?

I know the seal replacement is cheap and doable, but I don't have time for it atm.
 
Well... since then, I have developed an oil leak from what I believe is the front crankshaft seal (I assume this because there is wetness on the passenger side frame rail right below the front crankshaft area both directly underneath the belts/crankshaft and accumulating on the frame rail underneath the same area). There is maybe 2 to 5 drops of oil after every other time I drive (I drive for about 45 min at a tie), and never when sitting overnight. I know it is anecdotal, but... did the MMO clean the crud from around the seal, thus exposing the leak, and/or did the oil thin sufficiently to seep out of this exposed leak?

Since MMO is also capable of seal reconditioning, it is doubtful it is either the cause or cure in and of itself.

It would be impossible without a detailed examination to know what exactly initiated the seal leak.

If its that minor, deal with it until you can change the seal

Also... I bought Valvoline HM synthetic blend Maxlife for the impending oil change -it has seal revitalizer, I guess... should that suffice as a band-aid or should I add a bottle of the Blue Devil Stop Leak as well?

You may derive some benefit from the HM oil based on the overall condition of your engine but only a small possibility it will affect the leak. ( since the seal chemicals in MMO didn't stop it, odds are not looking good more of the same will but given the amount you added, a full dose may give some improvement)
 
Since MMO is also capable of seal reconditioning, it is doubtful it is either the cause or cure in and of itself.

I was not aware of this - the seal reconditioning properties of MMO. If that is the case, then perhaps a full dose is in order. However, would a full dose of the MMO thin the oil sufficiently to create a larger leak regardless?

Sounds like I'm going to have to set aside the time to fix that seal.
 
was not aware of this - the seal reconditioning properties of MMO. If that is the case, then perhaps a full dose is in order. However, would a full dose of the MMO thin the oil sufficiently to create a larger leak regardless?

I don't know the specific chemical or concentration by volume so that is unanswerable.

Also, a conditioner only restores pliability and bulk ( to a limited degree under certain conditions) so if your seal is mechanically damaged ( loss of mass, geometry, garter tension or sealing surface etc.) then nothing in a bottle is going to make it any better.

That's why I said do the O/C with the HM- if that concentration doesn't make a difference, more of the same with another brand is unlikely to either.
 
I have used MMO in many used cars I have owned and never had it cause a leak. However I have had leaks caused by using synthetic oil in a used truck and car that were high milage and previously ran mineral oil.
 
I second JB250's answer. Go back to mineral based oil. With the mileage that is on that engine, I would be using a 10w30 instead of a 5w.
 
I certainly wouldn't recommend 10w-30 over a 5w-30 with a Wisconsin winter fast approaching. The switch to 10w will do nothing for the leak.

I would try high mileage oil for the next interval and monitor. If the leak is slow, just drive it until you can replace the seal. Be sure you have the leak identified before you go replacing seals/parts on a whim, lots of places oil can come from.

I would be hesitant to use more MMO as it will thin the oil, which is not a good combo for leaky seals. I've not heard of MMO having seal conditioning properties, learn something new every day.

As another posted mentioned, do not add stop-leak to the crankcase unless it's an emergency.
 
When my old WIllys needed a fuel pump, but the twins needed diapers worse, I was gifted an old pump. Old enough to be put together with slotted screws, IT had been a known good used pump when put on a shelf 20 yrs previous. I unscrewed the halves and removed the dried out diaphragm. This, I soaked it in a jar of MMO overnight. Next afternoon, the Willys resumed its beach buggy duties and the pump worked 'til the end. :cool:
 
I know it is anecdotal, but... did the MMO clean the crud from around the seal, thus exposing the leak, and/or did the oil thin sufficiently to seep out of this exposed leak?

Also... I bought Valvoline HM synthetic blend Maxlife for the impending oil change -it has seal revitalizer, I guess... should that suffice as a band-aid or should I add a bottle of the Blue Devil Stop Leak as well?

I know the seal replacement is cheap and doable, but I don't have time for it atm.

There is such a thing as a "false" seal which is a dam of sludge, metal particles, and worn seal material that can surround a seal lip.

MMO contains mostly solvents and some phosphate to replace the phosphorus that it displaces when added to oil.

It is entirely possible that if you have a worn seal it could remove that false seal and cause a leak.

After having done a detailed analysis of MMO there was no indication that MMO contains any seal conditioners, regardless of the claims made by the manf. or by some of the incorrect info on Wiki.
 
That's interesting, thanks

I was biting my tongue in this thread but I had the thought the whole time, MMO has seal conditioners?

MMO is a lot like Kerosene. I was not aware it had any seal conditioners.

It used to be suggested to be used up to 20% in an engine for slow and steady clean-up and or sludge removal, probably held in suspension in the oil until drained. At least if I remember reading correctly. It smells a lot like kerosene.
 
Mola said:
MMO Analysis by University lab

(Any element 2 ppm or lower not reported)

Phos - 631 ppm Use: Anti-wear and Lead Scavenger for when gasoline had TEL

Potassium – 60 ppm Use: Buffer and weak detergent.

Viscosity – 2.3 cSt@100C , 7.9 cSt@40C; Comment: One very LV liquid! Due to light fraction Hydrocarbon Content.

Flash Point – 143F

TBN – 0.3

Glycol – 0.63

Oxidation – 10


Hydrocarbons:

Naphthenic Hydrocarbons - Use: Carrier and weak Solvent

Mineral Spirits - Use: Carrier and Medium Solvent, Low odor paraffinic solvent which is Dearomatized Kerosene

Chlorinated Hydrocarbons - (2) of orthodichlorobenzenes; Use: Strong solvent and decarbonizer
 
There is such a thing as a "false" seal which is a dam of sludge, metal particles, and worn seal material that can surround a seal lip.

MMO contains mostly solvents and some phosphate to replace the phosphorus that it displaces when added to oil.

It is entirely possible that if you have a worn seal it could remove that false seal and cause a leak.

After having done a detailed analysis of MMO there was no indication that MMO contains any seal conditioners, regardless of the claims made by the manf. or by some of the incorrect info on Wiki.
*Correct - my understanding is MMO is mainly a mixture of solvents , naphtha / mineral oil and a carbon softener - no seal conditioners . I use a small dose of MMO in the gas for my lawn mower for good measure along with an ethanol remover / fuel stabilzer which seems to keep things pretty clean and trouble free with the mower . For vehicles - it's Techron in the gas tank (regular maaintanence) and Rislone in the oil (if I suspect an issue with rings , etc.) Other wise , it's top tier gas and synthetic D1 / Gen 2 rated 5W30 oil I find on roll back at WM for 5K mile OCI's and call it a day
 
I was biting my tongue in this thread but I had the thought the whole time, MMO has seal conditioners?

MMO is a lot like Kerosene. I was not aware it had any seal conditioners.

It used to be suggested to be used up to 20% in an engine for slow and steady clean-up and or sludge removal, probably held in suspension in the oil until drained. At least if I remember reading correctly. It smells a lot like kerosene.

Don't bite too hard because its more of a semantics issue and basically me repeating "legendary claims" without due diligence.

I did ask both of my primary seal engineering vendors and got basically the same answer from both so I'll just compile and paraphrase.

Back in the day" when seals had a much higher natural rubber recipe, MMO did "swell" them somewhat and that started the claim of leak stopper and of course it stuck and MMO apparently didn't seem to want to change it (Its a Mystery as to what it does)- doesn't have near the same effect now.

Obviously, it does not have any ingredient that today would be any form of seal "conditioner"- more of a word play and illusion.

Just FYI
 
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