Question for Paul McBride, the General Aviation News engine expert: I always read your articles and now have a question for you: Does adding Marvel Mystery Oil to the fuel and/or engine oil help valves from sticking?
Don Lagarde, via email
Paul’s Answer: Ah, here’s an age-old question that has been kicked around for years.
I’ve heard comments from both sides claiming it’s good and it’s bad.
From my viewpoint Don, I’d choose not to use it because I don’t know that it would do any good.
There are better ways to prevent valve sticking such as frequent oil and filter changes, proper operating procedures, having the engine baffling in good repair, and making certain it’s doing the job it was designed for.
If you suspect possible valve sticking, I recommend you review Lycoming Service Instruction 1425A and Lycoming Service Bulletin 388C.
Now that you’re beginning to think I’m dodging your question, here’s my honest answer: I would not use Marvel Mystery Oil in my aircraft engine. I will admit that I don’t think it may cause any harm, but I’m not convinced that it would do any good either.
Anecdotal is correct in every respect, especially if the additive is not listed by the engine manufacturer as a “factory approved lubricant.” In such cases, whether FAA approved or not, its use is limited to the experience of the user.
I generally consider additives to be useful if the need is compelling. For instance, a flight school airplane accumulating 50 hours a month has little need for Camguard but the average GA owner might take a year or more to accrue that. For them, maybe an additive is worthwhile.
As the result of numerous shop inquiries, I had Camguard analysed in 2015 by a lab in Atlanta. The results at that time are as follows:
Iron 2
Chrome 1
Ni <1
Al <1
Lead <1
Co <1
Tin <1
Silver <1
Titanium <1
Silicone 1
Boron. 2
Sodium 16
Moly 9
Potassium. <10
Phosphorous 10,000
Zinc 5
Calcium 2,000
Barium <10
Magnesium 11
Antimony <30
Vanadium <1
Of particular interest is Phosphorus at 10,000 parts per million (PPM) in a single sample bottle. That element was heavily used in Zinc dialkyldithiophosphate (ZDDP), an additive package intended for automotive oils until its reduction began in the 1990s for emission reasons. It will protect the cam and lifters by offering a sacrificial coating reducing wear and protecting against corrosion. Does it work for everyone? Who knows. It’s still anecdotal.
A close work colleague used to work for Castrol as a petroleum engineer before it was taken over by BP. We asked him to do an analysis of this “Marvel Mystery Oil”. Tim came back to us and said ,It had automatic transmission oil in it ,turpentine , colouring and some thing else .[I,can’t remember ]
His recommendation was it was great for killing the weeds around the hangar . He waffled on about it effecting the base of an oil ???
I’ve always wondered about Marvel Mystery Oil…
I kept my 1953 C-170B outside on a dirt strip in North Pole, AK. In winter, it was routinely “cold-soaked” with temps below -30F.
Despite the conditions, I tried to take meticulous care of it, including wing covers & engine blanket, battery out, skis propped up on wood to keep them from freezing to the surface. I’d clean it off after heavy snowfalls, and I never put any liquids in it besides avgas & Phillips X/C oil.
I flew it in temps down to -10 F. I followed an extensive, time-consuming, pre-flight procedure, including clearing off any snow, ice, or frost while pre-heating the engine with my “Red Dragon” propane-burning heater. If required, I’d break my skis loose so I didn’t need to ‘power out’ of my spot when I started to taxi. I also didn’t push the throttle above idle until the Oil Temperature needle was in the green.
Meanwhile, ‘next door’ sat an older Citabria. It was usually half-buried in snow. If I hadn’t seen the owner, I would’ve guessed it was abandoned.
When he flew it, he’d pull the prop thru a couple times…I never saw him pre-heat it…then he’d smack any snow off his wings & stab (no covers) with a broom. He’d climb up on the struts, pour one quart (not ‘ounces’) of Mystery Oil into each fuel tank, and then one more into the engine. He’d get in & crank it (I have no idea what battery or starter he had) until it started to really bog down …& then it always fired! He’d idle it for maybe another 30 seconds, and then use full throttle to get it moving while blowing off whatever snow was still on his tail. He was usually airborne within 15 minutes of showing up.
Plane was still flying when I left after three years.
So …”Mystery Oil” …hmmm?
There is an episode of Jimmy’s World on YouTube. Jimmy removes the valve covers of a twin engine aircraft, and you can visually observe the lifters and valves are covered in gunk. Jimmy adds MMO to the oil of one engine, leaving the other engine without an additive. After X flight hours, Jimmy removes the valve covers for post flight inspection. The MMO treated side is visual cleaner. A significant difference. I don’t work for have stock in MMO.
You can’t see the valves or lifters by removing the valve covers. The rocker arms, and valve springs are all that are there.
Sad to say the proof is always anecdotal. Always someone can claim I got 40,00 hours out of my engine because I used xyz (Marvel Mystery Oil, Camguard, Avblend, etc).
Where is the independent research data over a reasonably long period of time?
MMO is an effective detergent additive. The question is whether you need to add a detergent to your engine. I’ve found adding some MMO to engines suffering low compression from piston ring leakage will often times free up sticky rings that are causing significant blow by, allowing me to avoid tearing down a customers engine for what is really an unnecessary top overhaul. I have effectively used MMO to free up some tired and sticky rings allowing as much as an additional 500 hours before needing additional attention to the engine. In one case cases, it allowed my customer to finish running out tired engine an additional 500 hrs before exchanging for a reman. I don’t use it as a regular additive, but as a tool to be used under certain circumstances.
MMO is mostly petroleum distillates and 1% TCP.
REF;
Marvel Mystery Oil (MMO)
primarily contains petroleum distillates (mineral oil/Stoddard solvent) as its base (around 70-90%), acting as a solvent and cleaner, with smaller amounts of Tricresyl Phosphate (TCP) for anti-wear and lubrication, plus trace amounts of dichlorobenzene isomers (ortho and para) and often a distinctive red dye and wintergreen scent for marketing, though some older reports mention lard.
Maybe Paul should add that owners should stop starting their engines for 10 minutes on the ground instead of flying the aircraft. This produces water that can not be burned out of the oil…….Oil must get to 180 degrees and the only way is the fly…..
BTW ethanol in auto fuel (many owners use it with the STC) is bad for aircraft engines above 5% …..Since most fuel at gas stations have 10%, it should not be used in aircraft engines….
How about aircraft engine oil that is half synthetic? Synthetic oil and the lead in 100LL will cause sludge to develop in aircraft engines……Remember Mobil AV-1…..100% synthetic oil,
a disaster …….
So……I do not see using MMO in any engine as dangerous and until the lead in aircraft fuel is gone, aircraft owners will still have valve and ring sticking in our engines……So….with a lead free fuel 100% synthetic aircraft engines oil can make a very successful come back!!
Thank you……..
Bottom line is it is not an approved additive for certified aircraft engines. It will, however correct most lifter taps on a car engine!
We have used Marvel in our planes for nearly 50 years now. Both in the oil and the fuel. All engines in all the planes – Pratt’s, Lycomings and Continentals….big and small bore both.
Having said that – frequent oil changes (25 hour max), proper operating conditions, inspecting filters and performing oil trend analysis is essential.
Adding the recommended 4 oz per 10 gallons of MMO can reduce the net octane rating to less than 80, so maybe not a great idea.?
I recently started using Alcor TCP, approved by both Lycoming and Continental, and It greatly reduced the lead deposits and also can scavenge existing lead-bromide.
The lead-phosphate has reduced the wear metals by 50%, with iron now 20 ppm.!!
oops, slipped a decimal point…so 4 oz will reduce the octane to 95-97, ok for low compression engines.
I’d still recommend TCP.
4 oz to 10 gallons = .4 oz per gallon.
I wouldn’t think that such a minute amount would lower the octane even one point.
petroleum distillates, like kerosene, have an octane rating of about 15. do the math.
For small Continental engines? YES. Adding MMO has proved helpful to decades of owners since the phase-out of 80 octane avgas.