Marvel Mystery Oil???

[cargoflyr69]

I have a buddy that operates a C-170 and he swears by Marvel Mystery Oil - that stuff in the red can from the automotive store. I think he puts a couple ounces per 10 gallons of gas in the tank and also adds some to the engine oil when he changes.

he is not an A&P, but an old timer that just as well should be. You know, someone who has been around GA all his life working on planes he has owned and restored, just never took the required tests.

Anyways, he says the Mystery Oil gets him up to and past TBO on just about every engine he has every had. Says it lubricates and cleans parts you just cant get to without tearing an engine down.

My question: Is this really true or just a snake oil remedy? What are the real advantages to running this in a small piston engine, disadvantages? would you ever run it in a higher compression/injected engine? and most importantly, what does the FAA think of this practice?

I have an Aeronca Champ and he says I should start running Mystery Oil in my tanks too......

 

[jasonwb]

ahh yeah.............. ol' marvel mystery oil. as a kid growing up on a farm, we called it "jesus in a bottle". never used it in an airplane, but i know a lot of people who swear by it in their cars and equipment.
good luck!
jb

 

[EMBATP]

marvel

i know a guy kinda like what you are talking about except that he has his a&p and has restored a number of airplanes, mainly champs....we talked about this once...basically i think the FAA tested this stuff once upon a time, and the impression i got was that they realized it does have some benefits. but they also dont realize exactly how it works or what it does, and so are reluctant to "approve" its use....liability i guess. but i like you have talked to guys that swear by it, but i am sure their operation of the engine may have something to do with it....i do recall one time i was about to go up with a student, and the fuel in the sumps was red....i asked the owner what was up and he told me he used it. i asked him to show me where it was approved and he could not....so no fly that day...

 

[svcta]

Some people swear by the MMO. I'd love to hear from someone with a really good answer to the question, but I foresee a bunch of ambiguity, 50/50 split of opinions, or the "it can't hurt, so what the hell" at the end of this.

I can't believe I'm about to do this. Forgive me..............

Thoughts, Avbug?

 

[cargoflyr69]

I just did a search of the NTSB website and there were a few accidents that alluded Marvel Mystery Oil.

the reports always said that "upon investigation the fuel sump exhibited liquid red in color with an oily consistancy"... "upon further examination an empty can of MMO was found in the trash can at the owners hangar"......

However, none of these reports directly blamed the MMO, just operator error. Sounds like those guys had too strong a ratio going.

 

[brett]

My MMO Experience

I had a cylinder that was obviously low on the Continental A65 on my Baby Ace. It felt "soft" when pulling the prop through. Did a compression check and sure enough one cyl. came in at 52/80 -- crap! (Leaking exhaust valve.)

My airpark neighbor who was helping me do the compression check said, "I have a suggestion. Before you pull the jug or spend a bunch of money, pour MMO in the top spark plug hole -- fill the cylinder completely and let it soak overnight."

Next morning -- big puddle of MMO on the hangar floor still a lot in the cylinder. Drained it out, did another compression check -- 69/80! Been flying it three months and about 10-15 hours, still going strong.

(Took 15 minutes idling to get it to quit smoking though first start after the MMO treatment.)

Also I had a C-172 that had a valve stick, bad. A&P IA did the rope trick and got it fixed. Engine had a strange sweet smell when I got it back and some traces of red here and there -- Hmmm. He said, "run MMO in the oil and gas from now on, but I didn't tell you do do it." Never had another valve prob.

 

[IFollowRoads]

MMO will turn into amber colored goo in a fuel tank. It will gunk up fuel lines and the carburetor bowl. When it gets thick enough in the carb bowl it will keep the float down, which will leave the needle valve open, which will flood the engine, cause a stoppage, and create a fire hazard. If you don't ball up the aircraft on the off airport landing, the fuel tanks will need to be pulled out of the wings and sloshed to get all the goo out.

Personal experience, working on a PA22 owned by an "old timer" who swore by Marvels "Mystery" Oil. I cleaned the fuel system by blowing a bit of paper towl soaked in MEK through the aluminum lines with compressed air... about 100 times per section. All the flex fuel hose was replaced. Sent the carb out for overhaul.

Thats if you treat your fuel with it.

In the crankcase, it does nothing for you at all. If you are changing your oil according to the engine manufacturers recommendations, there is no reason at all to waste more money on MMO. It doesn't help your valves, and if it did break something loose and bring your compression up you have no way of knowing what else starting floating around in there just looking for an oil galley to clog.

So my advice to you, with no ambiguity, is stay away from that garbage. It doesn't do a dam thing for you, but it sure can cost you.

 

[erj-145mech]

This is similiar to my limited experiences with Marvellous. Ask yourself, if this stuff is so fantastic, how come I haven't heard more about it?

We ended up spending weeks resealing the fuel tanks on a BT-13 after it was added as a "top lube" according to the owner who added it.

 

[Bus Driver]

Also I had a C-172 that had a valve stick, bad. A&P IA did the rope trick and got it fixed.

What's "the rope trick"?

 

[~~~^~~~]

Ahh the MMO debate. Another timeless classic.

For what it is worth.... After having several mechanics recommend MMO I started mixing some with the fuel on my aircraft and running a quart in the crankcase. The benefits as I see them are:
(1) Longer fuel bladder life (according to a recent Aviation Consumer Article on Fuel Bladders - not oil) oil protects rubber and plastic. This is particularly relevant if someone chooses to run auto fuel (which I don't). Auto gas can have ethanol and other additives that increase octance but which are harsh to old airplane parts not designed for its' use.
(2) Possibly better corrosion protection - depends on the oil you use normally and what additive package is in that oil.
(3) Smoother engine operation and longer valve guide life. In most reciprocating engines high thermal stresses are found at the exhaust valve guide. I am not sure if the smoother operation is due to better oiling of the lifters, or smoother operation of the valves through their guides, or both. But MMO does seem to give you noticably smoother operation.
(4) Less gunk build up on the exhaust valves, seats and guides. Theory is that the oil gets vaporized and keeps the deposits soft where they get blasted away. Today 100LL has more lead than the old 80/87. So this is likely more of a benefit in low compression engines designed for the 80/87 fuel (like mine).

The other side of the coin, although I have no data to back this up, it makes sense:

(1) Higher EGT's. Any oil will burn hotter than AVGas. In my airplane I typically adjust the mixture richer to keep the temperatures where I am used to seeing them in AVGas use. I know there are arguements that we should be operating lean of peak and that these temperatures don't matter, but for me a $35,000 engine installation is not something I'm confident experimenting with. So I burn an extra half a gallon an hour to keep things cooler.

Some have tried to analyze what is in MMO. The product was developed shortly after WWI and at that time phosphorous and zinc were used as "racing" oils. These provided lubrication under extreeme conditions and had cleaning properties as well. These products were phased out with the advent of catalytic converters in cars. Curious consumers have sent MMO off to labs and come back with the following reports (reportably from Blackstone's):

It is a light napthenic oil ( about 3 wt).
About 20% solvent-probably mineral spirits
Dye
790 ppm phosphorous
Wintergreen for smell

The solvent would tend to provide some cleaning ability, at low temperatures.
The low viscosity would tend to act as a detergent. The phosphorous probably provides an EP (extreme pressure) ability, or would tend to prevent scoring or seizure. This agent is already in most motor oils.

At lunch a couple of years back I had a couple of manufacturers' air safety engineers and NTSB IIC's at the table and asked their thoughts on MMO. I was surprised to hear that the tech reps say that they thought running MMO was a good idea for the reasons I outlined above. The NTSB Investigators said they had not seen an accident due to the use of MMO, but they had no opinion at all as to whether it was a good thing, or a bad idea.

So to wrap up - I think MMO is a good idea, particularly in engines designed for 80/87 gas. The newer and higher compression engines may not see as much benefit. In any case you would not want to run more than a couple of ounces per 10 gallons.

As far as the airplane "I Follow Roads" experienced, that sounds more like a really old airplane that had seen a good bit of auto fuel. From what we do know about MMO the properties of the stuff the type of contamination he described does not fit. In fact many farmers religiously use the product for systems that are going into storage as a preservative to keep them clean and reduce maintenance costs.