# Marvel Mystery Oil---One Shot Rehab for Old Engines?



## Mt.Power (Aug 11, 2021)

Once I worked for an industrial company, but in the office. My office was in the fleet maintenance building where I came into contact with lots of old mechanics. One guy had a muscle car hobby. He told me he added one quart of Marvel Mystery Oil at every oil change. Why, I asked? He once worked at an airport. A mechanic there bought an old bi-plane, the type used for crop dusting with a radial engine. Naturally, it was as old as the hills. The new owner, my informant said, filled up the whole crankcase with Marvel Mystery Oil and flew around the airport a couple times. Then, he drained the oil. All kinds of black crud streamed out, deposits from day-one operation. 

So, I tried adding one cup of MMO 50-100 miles before an oil change in my Toyota pickup. The same thing happened. The oil coming out was blacker than black. So I continued over the years doing this. Of course, after awhile the outgoing oil looked better and better.

The reason I am posting this is it is this is the plan for my newly acquired 1940s O'Keefe diesel generator. Is there any reason not to do this? Please school me.


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## iowagold (Jan 22, 2020)

yup a engine flush is a great idea!
a heads up just watch what you use as it can eat gaskets.

if you have the time a full rebuild is a great plan to get all of the old trash out.


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## Dutchy491 (Sep 18, 2019)

Mt.Power said:


> Once I worked for an industrial company, but in the office. My office was in the fleet maintenance building where I came into contact with lots of old mechanics. One guy had a muscle car hobby. He told me he added one quart of Marvel Mystery Oil at every oil change. Why, I asked? He once worked at an airport. A mechanic there bought an old bi-plane, the type used for crop dusting with a radial engine. Naturally, it was as old as the hills. The new owner, my informant said, filled up the whole crankcase with Marvel Mystery Oil and flew around the airport a couple times. Then, he drained the oil. All kinds of black crud streamed out, deposits from day-one operation.
> 
> So, I tried adding one cup of MMO 50-100 miles before an oil change in my Toyota pickup. The same thing happened. The oil coming out was blacker than black. So I continued over the years doing this. Of course, after awhile the outgoing oil looked better and better.
> 
> The reason I am posting this is it is this is the plan for my newly acquired 1940s O'Keefe diesel generator. Is there any reason not to do this? Please school me.


Well, didn’t you ask in another post about whether to use a detergent Oil or non-detergent Oil in this old old engine? Now you want to clean out the crud in one go? I think that you might cause more issues with a sudden shock treatment. Like I originally suggested just use a good synthetic but do quick changes to keep ahead of the possibility of a plugged Oil filter. Amsoil has a very good synthetic Oil that is gentle on older engines. It is not their premium Oil but it’s the best Oil to try in that old relic. I’ve had many customers with old diesel tractors that are very pleased with it. Why did I get these old tractors on synthetic? Because the new tractors they just purchased required synthetic Oil and the owners now wanted a synthetic in their old girls. That was a no no, Premium lube in old equipment. So I had them use this synthetic oil and they got easier cold starts, and longer drain intervals without Oil leaks. Win win. This is the Oil that I suggest you try. Heavy-Duty Synthetic Diesel Oil 15W-40 Amsoil ADP. Look it up or pm me for a link. Made in the USA and delivered to your door in a day or two. Dutchy


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## motormonkey (Jul 10, 2016)

Remember, the main purpose of engine oil is to LUBRICATE. So, how well does whatever flushing oil you're using lubricate? Likely not very well. Look at the instructions on any of the products labeled as, "flushing oils." They almost all caution to only operate the engine at idle and not under any load with that oil in the engine. There's a reason for that. Those oils won't provide adequate lubrication to the higher stressed parts in an engine.

Also remember that a "flushing oil" will likely cause deposits to break loose and get flushed downstream, possibly into critical areas, like rod and main bearings, where they can do serious harm.

And in an airplane engine??? Would you ride in an aircraft whose engine oil might not keep the engine running?

If those flushing oils had any real merit, they would be recommended by engine makers. There could be some exceptions where flushing oil might help in really old engines that are already crudded up, but ordinarily, the best policy is to forget the flushing oils, and regularly change the oil according to the manufacturer's recommendations.


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## exmar (Jun 29, 2015)

Lots of good info. I'll remind folks we're talking about a diesel, not gas. Yes, they both use lubricating oil, but different animals and diesels, by definition are heavier duty. Also, this is in a generator which, unless it's been at this cabin off grid for lots of years tend to be low hour units. I'd go with some MMO, let it get warmed up well, drain and refill with whatever the OP has decided for the long term. Also, I believe getting it running on whatever is in the crankcase was the next step, then an oil change. Seeing what comes out would be a good indication of what to do next.


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## Mt.Power (Aug 11, 2021)

The detergent-non-detergent thing was never an issue since circa 1965 nobody would have ever found non-detergent oil and most people would not know the difference anyway, so it was running on detergent oil. Stirring up an muddy pond, so to speak, is a real issue and one to think about here. I would guess this generator ran on 30 wt. diesel oil, if not then 10w-30. Back in the 1970s synthetics were said to shrink old seals not made for synthetics. I guess that problem is solved but if not this engine would be the one to fail. exmar may be right in that the prudent thing to do is drain the old oil first and try to determine where I am.


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## exmar (Jun 29, 2015)

80 year old engine, unknown hours, unknown maintenance, if it runs, put in "regular" oil and leave well enough alone?

Edit: Does this unit have a cartridge type oil filter? If so, visual of the old element will give you an indication of the attention the engine has received. Cheap insurance would be to increase oil and filter change frequency while you and the engine get to know each other. I think I'd go with a straight 30W or probably a 10W-30 synthetic.


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## iowagold (Jan 22, 2020)

oh yea is there an hour meter on this gen set?
thinking rust from sitting a long time...
that was why maybe a tear down...
diesel is hard to inspect the cyl unless you have the head off...

any one know if they were just copper or steel gaskets on the head??
they can corrode gaskets etc. over time unless the water was drained, or antifreeze as coolant was changed at a proper time..
even more so on the late model engines where mixed metals are used..

unless they used oil as the coolant!
yea some of the engines we have in the fleet use engine oil as coolant!
no kidding!
bad deal if you loose a head gasket on one of those...
diesel run away.....
we change the head gaskets every 10 years on those engines.

check the air filter and intake for trash first.
mice etc could have moved in on an old setup...
check wiring as well.
new oil, filter.
fresh fuel and fuel filters and clean the water separator.

if you have to use start fluid use it sparingly with out the air filter direct in the intake,
it does not take much to get them to start in the warm temps we have been having.
do not use the glow feature if it has it when using the start fluid.
oh yea if it has a block heater plug it in!
even in warm temps for first start up it gives it a head start!
we use even heat guns on the intake air to pre heat the air to over 100 deg f.
lots of tricks on starting diesel if it does not pop right off...
who knows it might be no hours???
but remote...
yea it could have a bunch of hours on it...

look at the exhaust inside to see if it has a layer of soot!
that might help tell how long it has been from last start..
and maybe on the hours as well...


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## Ground Fault (Jun 9, 2020)

I've used MMO on two 1800rpm Onan generators, back before there was such a thing as SeaFoam or Yamaha Ring-Free. Added 2-3 ounces to the oil the last fifteen minutes before oil change, during which time I sprayed the MMO directly into the air intake before changing the oil (as "directly" as possible in them: both had tortuous labyrinths of an intake path, probably for sound dampening). Ran until they stopped smoking indicating the "cleaning" was "complete", then changed the oil. I change the oil at 75 hours...it's just not that big of expense to do so. As referenced in the posts above, it was BLACK, even at just 75 hours. The change in oil color after MMO treatment was significant, bespeaking its enhanced effectiveness in flushing hydrocarbon deposits versus detergent oil alone. As for it damaging rings and bearings...it cleans at the molecular level _just like oil does_, producing a colloidal solution of suspended hydrocarbon_ molecules_, not chrystalline shards of hydrocarbon grit. Aren't these hydrocarbon molecules already suspended in the detergent oil anyway, from the first hour of use after an oil change? Is a "few" turns of the crank in a MMO-enriched oil solution worse than many turns without it, weighing in the balance the benefit of de-carbonization? If it did damage gaskets or seals you would expect it to first become evident at the crank seals. Neither ever wept a drop.

I once worked next door to the Onan servicing dealer in our area and became good friends with the owners. I often hung out there during lunch hour and learned much about their servicing. Onan gensets are famous for needing a decarbonization at around 400-450 hours. VERY uncharacteristic of the 1800rpm Onan, I have never had to do a head-off decarbonization job on either. I am attributing that to the MMO. I ran dino oil in both. The first had over 1200 hours on it when I sold it to my buddy. It is still powering travel trailers in a deer camp out in the hill country, having long ago been "salvaged" from the motorhome containing it. (The motorhome is still there but derelict. They use it only as a "powerhouse" containing the genset, along with one of the two gas tanks.) The second I still own, it out there in the shop. I hope to resume using it when I retire.

I believe in Marvel Mystery Oil on low rpm small engines.


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## iowagold (Jan 22, 2020)

Ground Fault said:


> I've used MMO on two 1800rpm Onan generators, back before there was such a thing as SeaFoam or Yamaha Ring-Free. Added 2-3 ounces to the oil the last fifteen minutes during which time I sprayed it directly into the intake before changing the oil (as "directly" as possible on them: both had tortuous labyrinths of an intake path). Ran until they stopped smoking indicating the "cleaning" was "complete", then changed the oil. I change the oil at 75 hours...it's just not that big of expense to do so. As referenced above, it was BLACK, even at just 75 hours. The change in oil color after MMO treatment was significant, bespeaking its enhanced effectiveness in flushing hydrocarbon deposits versus detergent oil alone. As for it damaging rings and bearings...it cleans at the molecular level, producing a colloidal solution of suspended molecules, not chrystalline shards. Aren't these hydrocarbon molecules already suspended in the detergent oil anyway, from the first hour of use? A "few" turns of the crank in a MMO-enriched solution worse than many turns without it, weighing in the balance the benefit of de-carbonization? If it did damage gaskets or seals you would expect it to first become evident at the crank seals. Neither ever wept a drop.
> 
> Ran dino oil in both. VERY uncharacteristic of the 1800rpm Onan, I have never had to do a head-off decarbonization job on either. I am attributing that to the MMO. The first had over 1200 hours on it when I sold it to my buddy. It is still running a deer camp out in the hill country, having long ago been salvaged from the derelict motorhome containing it. The second I still own, it out there in the shop. I hope to resume using it when I retire.
> 
> I believe in Marvel Mystery Oil on low rpm small engines.


did that onan have a spin filter like the late model rv units do?


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## pipe (Jun 27, 2021)

From MMO MSDS
Component CAS Number Concentration (wt%) 
Petroleum Distillates (Hydrotreated Heavy 64742-52-5 60-100% Naphthenic) 
Petroleum Distillates (Stoddard Solvent) 8052-41-3 10-30% 
Tricresyl Phosphate 1330-78-5 0.1-1.0% 
Ortho Dichlorobenzene 95-50-1 0.1-1.0% 
Para Dichlorobenzene 106-46-7 <0.1% 

As you can see, MMO is mostly mineral oil and paint thinner








Marvel Mystery Oil - Wikipedia







en.wikipedia.org





White spirit or mineral spirits, also known as mineral turpentine, turpentine substitute, and petroleum spirits, is a petroleum-derived clear liquid used as a common organic solvent in painting. There are also terms for specific kinds of mineral spirits, including Stoddard solvent and solvent naphtha


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## Dutchy491 (Sep 18, 2019)

FYI, PAO synthetic lubes like Amsoil swell Oil seals not shrink them and also have high detergent characteristics and high TBN numbers to offset acidity. Dutchy


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## Ground Fault (Jun 9, 2020)

Yes, both had a screw on filter. My memory is a little foggy, and I'm too lazy to go out there and get one to look at, but I think they were either a Fram 3614 or a 1251. There is every chance that I am wrong on both. They are located in such a way as to make a royal mess when you change them. I also cleaned the air filter at 75 hours, replaced at 150 hours. I still own the points and condenser, spark plugs and carb rebuild kit for the first one. Compared to the howl of other generators, I love the hum of a Onan genset!


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## Mt.Power (Aug 11, 2021)

There was a paper taped to the side of the generator indicating service in 2007. WIX fliter 51006, WIX fuel filter 33032. These are still availiable. The fuel tank obviously did not work. There was a hose coming down to a container of diesel beside the generator, through the spout area of the container. It allowed air to come in an out so I am thinking that may be bad diesel now. So now we plan to take up a gallon of diesel and switch the hose to that. If I am doing that, maybe some injector cleaner in that gallon of diesel would be the first thing to do. Right now I am most interested to just see if it starts so Iowagold, those were great suggestions. Maybe even MMO in the diesel fuel as injection cleaner?


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## iowagold (Jan 22, 2020)

Ground Fault said:


> Yes, both had a screw on filter. My memory is a little foggy, and I'm too lazy to go out there and get one to look at, but I think they were either a Fram 3614 or a 1251. There is every chance that I am wrong on both. They are located in such a way as to make a royal mess when you change them. I also cleaned the air filter at 75 hours, replaced at 150 hours. I still own the points and condenser, spark plugs and carb rebuild kit for the first one. Compared to the howl of other generators, I love the hum of a Onan genset!


i would love to see if oil magnets would to have worked well for the onan setup for you.
I have those on a clients modern onan (2013 new)
and the oil stays clean for the oil changes.
pan drain plug oil magnet as well as the spin oil filter magnet.

I have cut open the filter and seen the trapped trash!
oil change at 200 hours.
it is ran at the state fair for hours on end.
they camp in a private lot just off the main camp ground.
pretty cool!
they get water sewer from the city!
and have a large fuel tank in the back of the pickup to refuel the gas tank in the LARGE toy hauler camper.


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## iowagold (Jan 22, 2020)

Mt.Power said:


> There was a paper taped to the side of the generator indicating service in 2007. WIX fliter 51006, WIX fuel filter 33032. These are still availiable. The fuel tank obviously did not work. There was a hose coming down to a container of diesel beside the generator, through the spout area of the container. It allowed air to come in an out so I am thinking that may be bad diesel now. So now we plan to take up a gallon of diesel and switch the hose to that. If I am doing that, maybe some injector cleaner in that gallon of diesel would be the first thing to do. Right now I am most interested to just see if it starts so Iowagold, those were great suggestions. Maybe even MMO in the diesel fuel as injection cleaner?


maybe add a modern water separator as an upgrade after you find out what you have...
I will pm the details.


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## Ground Fault (Jun 9, 2020)

Paul, you reference oil magnets. Look what showed up in my mail today:


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## Mt.Power (Aug 11, 2021)

That is a great idea, putting a magnet on an oil filter. I put them on drain plugs regularly. I have a tiny rare earth magnet on my Duromax generator's drain plug. Do you have any link Ground Fault?


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## tabora (Sep 6, 2018)

Mt.Power said:


> That is a great idea, putting a magnet on an oil filter.


Take apart an old PC disk drive. There are several small, extremely powerful rare-earth magnets in each one. Stick two or three on the oil filter or the oil drain plug. I have hundreds of them on our refrigerators, OPE and metal cabinets for holding notes, etc. My clipboards each have one on the clip to hold a pen by the metal pocket clip.
















Salvage Neodymium Magnets from an Old Hard Drive | Make:


Learn how to locate and salvage super-strong rare-earth magnets from an old, broken hard drive.




makezine.com


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## Mt.Power (Aug 11, 2021)

There are two in each microwave but they are kinda large.


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## iowagold (Jan 22, 2020)

Ground Fault said:


> Paul, you reference oil magnets. Look what showed up in my mail today:
> View attachment 9884


there ya go!
the real corvette club magnet!

did you also see the wrap around the filter style?


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## iowagold (Jan 22, 2020)

Ground Fault said:


> Paul, you reference oil magnets. Look what showed up in my mail today:
> View attachment 9884


pm me if you need links for those oil filter magnets.
and other styles as well.
we use those on the dodge and chevy trucks diesel oil filters.
they work well in the fleet!
snaps right on the end of the wix filter.


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## Ground Fault (Jun 9, 2020)

Amazon.com: Corvette Oil Filter Magnet Fits: All Corvettes : Automotive Magnet link

Paul I did see the wrap magnets. I would have bought them too but I have other magnets that I put on the sides. Got them from K&J Magnets. These Corvette Club magnets are very tenacious. The magnets you can buy to locate a firearm underneath a desk are even more tenacious. They would work too, and with greater magnetic field to leach further up into the oil filter.


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## JRHill (Nov 19, 2020)

Dutchy491 said:


> Well, didn’t you ask in another post about whether to use a detergent Oil or non-detergent Oil in this old old engine? Now you want to clean out the crud in one go? I think that you might cause more issues with a sudden shock treatment. Like I originally suggested just use a good synthetic but do quick changes to keep ahead of the possibility of a plugged Oil filter. Amsoil has a very good synthetic Oil that is gentle on older engines. It is not their premium Oil but it’s the best Oil to try in that old relic. I’ve had many customers with old diesel tractors that are very pleased with it. Why did I get these old tractors on synthetic? Because the new tractors they just purchased required synthetic Oil and the owners now wanted a synthetic in their old girls. That was a no no, Premium lube in old equipment. So I had them use this synthetic oil and they got easier cold starts, and longer drain intervals without Oil leaks. Win win. This is the Oil that I suggest you try. Heavy-Duty Synthetic Diesel Oil 15W-40 Amsoil ADP. Look it up or pm me for a link. Made in the USA and delivered to your door in a day or two. Dutchy


Throwing MM oil in an old engine (that never saw it before) is _NOT_ a good thing. You could put a glug in at an oil change (I mean a very small glug, 1 oz) and add a _little_ bit to the fuel. I love MM Oil. Good stuff. Smells good too. But don't add it to an old unit and think it will be revival time. If you rebuild the engine then yes, a couple oz of MMO at oil intervals would be good. If you run synthetic then just a few oz in a gallon of good fuel, none in the oil.

These days I haven't seen a single small engine that specifies non-detergent oil even though they have no filtration. But times are different. People know to change their oil at intervals. I run synthetic in EVERYTHING. I have a magnetic plug in EVERYTHING. Oil comes out clean and there's rarely anything on the magnet. Based of that I have doubled the oil change intervals and the oil comes out about the same. But I only do that on stuff that I broke in from new. Never on an older engine.


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## Mt.Power (Aug 11, 2021)

I have pretty much decided not to do the MMO thing in this situation.


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## Ground Fault (Jun 9, 2020)

Last night I watched a recorded episode of _Engine Power _where they added a half a can of Seafoam to the oil in an old Ford 300cu.in straight six that they were doing basic changes to on the dyno so as to proof if those "urban legend" changes actually improved performance. After adding the SeaFoam they ran it at 25% load at 2500 rpms for 30 minutes, then changed the oil. Black as night. Then they did it again. Came out much less dark. I think it yielded 3hp and equivalent torque increase, which is inside the margin of error. It didn't blow up or harm it, only cleaned it, judging by the appearance under the valve cover. (In a subsequent episode they put a turbo on it and made almost 600HP and almost 600ft/lb torque at 14lb boost.) Sounded like it was loafing...


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