Marvel mystery oil in fuel

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I use it regularly in my older cars, boat and other machines with metal fuel tanks.

A long time ago, when I first started driving and had a TR6, the local British car guru strongly recommended MMO, but not for any engine benefits. I grew up near the water and British cars of the era (I'm sure others as well) had an issue where the fuel tanks would rust at the high water mark especially in seasonal use cars. TR6's seemed especially vulnerable to this, at least that was my experience. The mechanic's theory was that the MMO in the fuel would leave a more oily film from sloshing then non treated fuel. This makes some sense to me and I have never had a problem w/ fuel tank rusting since then.

I have been meaning to test the theory with some bare metal strips hung in our lake house shed.
 
I've been continuously using MMO per directions(1oz/2.5gals) in my Firebird(OPE) every fill up for many years without issues. However, this car has no sensors to trigger CELs. The carb seems to like it.

I've also tried it in my wife's Lexus RX(on several occasions) and it triggered the CEL every single time w/o fail even w/lower doses. This engine triggered a CEL even w/FSCs. Could have just been our example being fussy.

I have also tried MMO in other computer controlled vehicles(on a very limited basis) w/o issues. But I'm not sure of the benefits in modern engines.

What was the code?
 
Used it frequently in older cars; not sure if there's a benefit in using it in new ones or not. It seemed to make quite a difference when used in the fuel of an '07 Chevy Aveo we had way back when (1.6L E-Tec II I-4). Noticed increased MPG, no fuel related issues, fuel line seemed relatively clean. Squeezed almost 200K miles from that econobox before passing it on; whether MMO had much to do with that is open to question.

New owner is still driving it around, so...maybe?
 
some engines "Like" it. As example my old S10 truck and 2002 BMWr1150RS got better mileage using it. The BMW picked up 2 miles per gallon consistently. My newer BMW and my Buick do not care.

On the BMW I kept the marvel mystery oil in a small backrest bag in a 5 oz recycled codeine cough syrup bottle. I had just refilled it when it was stolen. I would love to have seen the video when the druggie drank it.

Rod
 
Originally developed to keep the high lead content in gasoline from forming deposits in the carburetor and elsewhere. So it is a solvent that works on lead. I imagine that it works on other deposits also. I'm a little worried about the lead in the bearings if used in the crankcase.
 
Is it worth adding marvel mystery oil to my fuel tank every other fill up or so as a schedule maintenance plan? I have no fuel problems I'm just wondering if it's worth it to prevent problems arising in the future. Thanks for your help.

No waste of money
 
Back in the 50`s an older mechanic said MMO was useful in overhead engines with extra lube in valve guides. He also added a pint to the crank case 500 miles before OC.
 
Is it worth adding marvel mystery oil to my fuel tank every other fill up or so as a schedule maintenance plan? I have no fuel problems I'm just wondering if it's worth it to prevent problems arising in the future. Thanks for your help.
Using MMO every other fill up is an excellent way to extend the life of the rings and cylinders. And MMO will be neutral or help the crankcase oil as it is forced into and past the piston rings. Some chemicals in strong fuel additives will adversely affect the motor oil in the ring-cylinder area.
So use the MMO regularly, and the chemically strong additives such as Techron, BG 44K, Berryman's B-60, and the like once per year. Also you can add some MMO, like 4 ounces to the motor oil, a couple of days before an oil change.
 
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