I put a gallon of MMO in my gas tank...

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Just for S&G I put a gallon of Marvel Mystery Oil in my ~30 gallon gas tank of 1995 Chevy Tahoe before fill up.

It was going great and smooth, until 40 miles into the gas tank... The misfires started... Multiple misfires, and OBD1 only gave code 32 (EGR code). Over the last couple tanks misfires kept getting worse, even the slightest incline caused a couple downshifts to help the ol´ 5.7L pull the heavy Tahoe.

Today took out the OEM AC Delco plugs that I installed about 10k miles ago and found them to be very wet, most likely with MMO, as it is an oil and doesn't burn off as fast as gas. Replaced the copper AC Delco plugs with NGK Platinums... All I can say is I should've got these plugs to begin with, because the engine is MUCH smoother now. Misfires obviously gone. Engine is smoother than it was before the misfires, and smoother than it was with brand new AC Delco copper plugs.

Moral of the story? Don't put a gallon of MMO in your gas tank, unless it is a 100 gallon fuel tank. 1qt is plenty for preventative maintenance. I just wanted to see what severe overdose will do and it did exactly what I expected it to do.
 
"Moral of the story? Don't put a gallon of MMO in your gas tank, unless it is a 100 gallon fuel tank. 1qt is plenty for preventative maintenance. I just wanted to see what severe overdose will do and it did exactly what I expected it to do."

Moral of the story is: Find better things to do with your time and money.
 
a gallon of MMO probably isn't a lot for a 30-gal gas tank, even though it is much more than you should use!

It is like putting 2 quarts, a half gallon, in a 15-gal tank, which is around the size of most cars' tanks.
 
You can put a couple drops in an air tool, like a 1/2 inch impact
wink.gif
 
If you had added it gradually so it had time to mix....

instead of all settling on the bottom,

it probably would've been OK.

Originally Posted by expat

Moral of the story is: Find better things to do with your time and money.


Yeah, pretty much
 
Originally Posted by dave123
You can't fix stupid.

It was an experiment: my time, my money, my consequences. Absolutely no reason to start the name calling, bud.

The point of any experiment is to find PROs/CONs of an idea. In this case CONs outweighed the PROs, so I am sharing my experience in case someone out there decides to do the same and hopefully stumbles across this thread.
 
Originally Posted by Linctex
If you had added it gradually so it had time to mix....

instead of all settling on the bottom,

it probably would've been OK.

I added MMO when the tank was nearly empty and topped it off with 26 gallons of fuel. Should've been pretty mixed up at that point.
 
That's an experiment I wouldn't have to do to know the outcome. Let the flame war begin.........................
 
Originally Posted by Vladiator
Just for S&G I put a gallon of Marvel Mystery Oil in my ~30 gallon gas tank of 1995 Chevy Tahoe before fill up.

It was going great and smooth, until 40 miles into the gas tank... The misfires started... Multiple misfires, and OBD1 only gave code 32 (EGR code). Over the last couple tanks misfires kept getting worse, even the slightest incline caused a couple downshifts to help the ol´ 5.7L pull the heavy Tahoe.

Today took out the OEM AC Delco plugs that I installed about 10k miles ago and found them to be very wet, most likely with MMO, as it is an oil and doesn't burn off as fast as gas. Replaced the copper AC Delco plugs with NGK Platinums... All I can say is I should've got these plugs to begin with, because the engine is MUCH smoother now. Misfires obviously gone. Engine is smoother than it was before the misfires, and smoother than it was with brand new AC Delco copper plugs.

Moral of the story? Don't put a gallon of MMO in your gas tank, unless it is a 100 gallon fuel tank. 1qt is plenty for preventative maintenance. I just wanted to see what severe overdose will do and it did exactly what I expected it to do.


Is your name Scotty Kilmer?
 
Originally Posted by Vladiator

Moral of the story? Don't put a gallon of MMO in your gas tank, unless it is a 100 gallon fuel tank. 1qt is plenty for preventative maintenance. I just wanted to see what severe overdose will do and it did exactly what I expected it to do.


Maybe it isnt all about the new plugs. Maybe MMO cleaned up some gunk for you that fouled the old plugs. That gunk may have prevented the engine from being as smooth and now that it is gone that is contributing to the noticeable improvement in engine running.

To know for sure, I think you should do it again and see if you can reproduce the results.
 
Originally Posted by Vladiator
Just for S&G I put a gallon of Marvel Mystery Oil in my ~30 gallon gas tank of 1995 Chevy Tahoe before fill up.

It was going great and smooth, until 40 miles into the gas tank...



Hmm---so you got more "S", and less "G". Tom Taylor always needs stories for the RockAuto newsletter . . .
 
Last edited:
It probably did do cleaning, there is that.
It has pale oil and mineral spirits to dissolve varnish, attempt to hit carbon, etc.
Just the plugs, so engine is fine.
 
Originally Posted by oil_film_movies
It probably did do cleaning, there is that.
It has pale oil and mineral spirits to dissolve varnish, attempt to hit carbon, etc.
Just the plugs, so engine is fine.

Yes, it probably did some cleaning. From what I've heard, a PEA based cleaner would have been more effective (both cost-wise and cleaning-wise). I put one bottle in each vehicle once a year. Haven't had a sticky injector yet.
 
A before and after bore scope would have been interesting. You most likely did a great clean up. Why not dump a gallon of a 2 stroke oil and compare? I have run 32 to 1 Gas mix of 2 stroke oil in my lawn mower because I brilliantly ran out of gas and all I had was the 2 stroke oil and gas can full.
 
Originally Posted by Donald
Originally Posted by Vladiator
Just for S&G I put a gallon of Marvel Mystery Oil in my ~30 gallon gas tank of 1995 Chevy Tahoe before fill up.

It was going great and smooth, until 40 miles into the gas tank... The misfires started... Multiple misfires, and OBD1 only gave code 32 (EGR code). Over the last couple tanks misfires kept getting worse, even the slightest incline caused a couple downshifts to help the ol´ 5.7L pull the heavy Tahoe.

Today took out the OEM AC Delco plugs that I installed about 10k miles ago and found them to be very wet, most likely with MMO, as it is an oil and doesn't burn off as fast as gas. Replaced the copper AC Delco plugs with NGK Platinums... All I can say is I should've got these plugs to begin with, because the engine is MUCH smoother now. Misfires obviously gone. Engine is smoother than it was before the misfires, and smoother than it was with brand new AC Delco copper plugs.

Moral of the story? Don't put a gallon of MMO in your gas tank, unless it is a 100 gallon fuel tank. 1qt is plenty for preventative maintenance. I just wanted to see what severe overdose will do and it did exactly what I expected it to do.


Is your name Scotty Kilmer?

thumbsup2.gif
 
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