Is Marvel Mystery Oil Safe For Use In Diesel Engines?

One of the more common questions I've been getting related to MMO this past year here on my previous video. I knew that is was from personal experience but when I came across this old gallon sized container from the 90's I realized that it had the answer still written on it!
YES! This stuff works just as well, and with modern low sulfur diesel, even better than it did in the 90's.

[dannywilliams]

Marvel Mystery Oil is the greatest thing ever. I pour it on my Cheerios every morning.

[tinkmarshino]

Been using this oil as far back as I can remember.. probably started in the late 60's or early 70's.. Great stuff..

[joseayala]

My 7.3 power stroke loves this. I only use it in the tank. 4 years with my truck and no problems so far.

[joeuscanga]

As a De-carbonizing agent:
Before changing a fuel filter, run the engine to temperature for about 30 min.
Shut engine off, remove old fuel filter, and empty fuel.
Re-fill the entire fuel filter wit MM-Oil, re-start the engine and run it for 1 1/2 minutes MAX.
Shut the engine for 2-3 hrs and let the MM oil sit on the injection system, injectors and let it soak
the combustion chamber & the top of the pistons.
( I personally let it soak overnight ).
Re-start the diesel engine 3 hrs later.
Let it run rough, until the engine idles smooth again.
Don be afraid by the rough idle and all the "whitish smoke" coming out the tail pipe, that's
what is supposed to do.
Run it for 30 minutes, replace the fuel filter with a new clean one.
Repeat once every 6 or 12 months. Your newly clean "De-carbonized" piston rings will love it and seal better.
After that, you will see a difference in engine responsiveness and torque.
If you have DPF, it is advised to remove it before doing this, then re-attach it after cleaning the fuel system on your equipment.
It might be a good time to soak and pressure wash the DPF can overnight anyway ( Once a year DIY Maintenance ).
It works...💯 %

[okhotrodder]

Mmo is great for airplanes also. When people ask me about putting a cleaner in their diesel, I tell them just grab some mmo and it'll clean after a few oil changes better than any other cleaner on the market and does great at cylinder lubrication.

[CrownRoyal]

I've use it in my 2017 Duramax
Great product.

[lesgobrandon]

The Cherry flavored fuel has 200 ppm sulfur I believe.

[franknew]

I have been using Marvel Mystery Oil in the gas of my car, truck, and lawn mower at every fill up since 2016. Everything is running great, and my car gets at least an extra 1.5 to 2 more miles per gallon on the highway.
Several years ago, my 2002 Chevy truck had a loud lifter ticking noise. It was a quart low on oil, so I added a quart of MMO to the crankcase. Soon the lifter ticking noise disappeared. I drove the truck about 400 miles and when I changed the oil, it was filthy. This was telling me that the MMO was removing some of the sludge out of the engine.
You were lucky to find four gallons of MMO in cans at a flea market. I was wondering how long the shelf life might be on MMO, and I assume it is still good. About a year ago, I saw an empty gallon can for sale at the Daytona Beach, Florida, flea market. I was tempted to buy it as a conversation piece, but it was very rusty, so I didn't buy it.

[timothydonahue]

I put 20 oz per hundred gallons of diesel in my Detroit diesel. It increases MPG from 5.6 mpg to 6.0 MPG. Which is an extra 60 miles per 150 gallon fillup. Or about $15 dollars per day on a 450 mile run.

[hometechnc]

From the FAQ page on Mystery Oil's website, regarding whether the product can be added to diesel fuel: Yes, you can use MMO in diesel fuel as well as gasoline. Use the same amounts as the gasoline treatment recommendations-4ozs of MMO for every 10 gallons of fuel. However, MMO should not be used in diesel engines where low sulfur content diesel fuel is required as MMO will raise the sulfur level in the fuel by 1 part per million. We are required to state this to comply with federal EPA laws. <> so, they are recommending it, but CYA on the legalities ?? Just wondering if will prolong the life of my 2024 Ford F350 6.7 ?

[darrellfincher]

added even to my chainsaws plus my 4 wheelers really helps on the carburetor issues keeping clean

[AndrewHCann]

Yes great to also works super and much more than 91 octane gas and unstuck a super tight motor that stuck to! Does 100% lube too !

[craigbrown]

Mechanic In a bottle. That's what I was told 30 years ago. I've always kept this in my garage. I put it in all types of motors. Now I'm primarily using it in engine oils. I agree it would be better used in diesel fuel then gasoline. In my opinion there are better gasoline additives for today's more modern engines.

[samuelbonacorsi]

On my bottle of diesel it says mmo does not meet the 15 ppm low sulfur requirement for modern diesels. It might be bad for the exhaust system? This said, I use it in all my older tractors.

[bro.weaver]

I perfer MMO in the METAL CAN, I can't tell you how many times the large plastic container cracked and woosh all over the place.

[davidg]

That stuff is goid forany things/uses.As always thanks for the video Erik, David.

[JohnGamerlTHEROYALBAVARIAN]

Curious. Did the MMO ingredients change sence the new bottles no longer mention use in diesels. I can't imagine them not putting it on there if nothing changed.

[ericdee]

What ever happened to Diesel #1? havn't seen that stuff in decades!

[PsRohrbaugh]

Newer diesels are very picky, because they're very high pressure. Older diesels were 3000-4000 psi. Newer diesels are much higher (don't remember the exact numbers, but call it 20, 000 psi).

[brentmcmahon]

It does talk about diesel that it will raise sulfur 1PP if used as directed but triple the dose to get your sulfur up to a good level in 05 Dodge 5.9 cummins and I add a quart in my oil before my oil change and I drive a 100 miles and drain my oil to cleans my motor up from the inside !