Marvel mystery oil in fuel

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98
Location
Nevada
Thread starter
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.
 
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2,176
Location
Flaherty, KY
I don't think it will hurt or help. That said, I use it from time to time (certainly not every other fill-up, maybe once per oil change) and always add a little in the gas cans I use for my OPE. Can't say I've noticed any difference before or after, nor do I expect to.
 
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3,289
Location
St. Charles County, Missouri
Had a bottle. Threw some in the fuel, threw some more in the oil before a change. Didn't hurt, didn't help--although I didn't tear it down or scope it so maybe it did. Usually use PET cleaners--Gumout or Techron. Don't know if they help either since I use Top Tier.
 
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Messages
12,782
Location
ROCHESTER, NY
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.
 
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7,494
Location
Mahzurrah!
My Jeep loved the stuff, ran it for years. It actually ran smoother with it and mpg went up a bit too. This was a very old school glorified tractor engine I-6 though. I tried it in more modern vehicles and saw no benefit, in fact mpg went down in a couple. So I didn't use it there anymore.
 
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987
Location
NC
2000 Honda CRV: If I stick to 4oz per 10 gallons of gas - then no MPG gain, but engine does seem to be smoother while I work it through the gears. If I do heavier dosage (like a pint per tank of gas) then it still feels smooth, but a bit more sluggish. In a small Honda engine every horsepower gained or lost is VERY noticeable. 2006 Toyota Camry V6: Added anywhere between 4oz per 10 gallons all the way to a full bottle to tank of gas. Never noticed any difference as 1MZ is already a silky smooth engine, no MPG gains. 2010 Volvo XC70: Haven't tried MMO in it yet. Will try once I fix the alternator gear... Some of my previous cars gained MPG though, when the recommended dosage was followed. Some of these cars: - 2005 Nissan Altima 2.5L, - 2001 Honda Civic 1.7L - 2002 Honda Civic 1.7L - 2001 Lexus IS300 3.0L - 2004 Lexus IS300 3.0L - 2009 Toyota Tacoma 2.7L - 2009 Scion xB 2.4L - 2003 Pontiac Vibe 1.8L - 2006 Pontiac Vibe AWD 1.8L - 2000 Lexus GS300 3.0L - 2006 Toyota Highlander Hybrid 3.3L AWD - 2006 Volvo XC90 2.5T AWD - 2013 Volkswagen Tiguan 2.0T AWD - 1995 Chevrolet Tahoe 5.7L 4x4 (On this one I once added a gallon of MMO to 30 gallons of fuel just for S&G. That was a disaster.) There were also a few cars that lost MPG no matter the dosage. But if dosage was followed - every car replied in smoother flow through RPMs, and some (not all) even had better throttle response.
 
Messages
861
Location
New York
I doubt it does much in the era of top tier gas. But I consider it a mild detergent additive and I use it on an older car on occasion as it might supplement stronger stuff like Gumout or Techron using after a tank full of the above, and I add it to small engine gas every so often...
 
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8,871
Location
Marshfield , MA
I haven't used any yet in the Camrys, but my OPE uses about a bottle per yr in the fuel. My EFI BMWs, it depended. wife's '86 528e responded so much, wife noticed. Used it in my '88 and it lowered MPG by a bit. Last few yrs, I winterized the 20w50 by adding a pint to the oil, Car started fine. So I did for the last few yrs I had it on the road. grin2
 

03s

Messages
127
Location
St. Catharines Ontario Canada
Have been using Marvel Ultimate Fuel & Motor Treatment last 2 oil changes. Added to both oil and fuel with 1/2 a bottle to oil and 2 ounces to 5 gallons of gas. Keeps it running smoother and quieter, never used MMO so I can't say the difference.
 
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5,667
Location
Tn.
I have used MMO in cars and lawnmowers,and to clean guns, hey, worked ok IMHO, did not mess up anything......hey, some folks even was their cars in dish washing detergent,,now what...lol
 
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Messages
244
Location
Occupied California
I had a 2009 Nissan 370Z. A known issue was the gas gauge not showing full even if the tank was filled to overflowing. From discussions on the 370Z Forum it was suggested that adding some MMO to the tank every few fill ups would solve the problem. I always used top tier 91 octane gas for the life of the car. But apparently the floats in the tank would get sticky and fail to read properly. When they did, I added about 8 oz. of MMO to a near empty tank and at the next fill up, the fuel gauge would read properly. It must have the right amount of solvent and lubrication properties to fix that kind of problem. I now use it every few tankfuls in my 2019 Mazda CX 5 turbo. It's not expensive and I figure it is good for preventive maintenance. The gas here in CA has who knows what done to it that causes problems, even the top tier gas. I use the same 91 octane in my Mazda, either Arco, Chevron or Shell brands. And I add a bottle of Techron about 500 miles prior to each oil change as well.
 
Messages
2,914
Location
GA.
Originally Posted by andyd
I haven't used any yet in the Camrys, but my OPE uses about a bottle per yr in the fuel. My EFI BMWs, it depended. wife's '86 528e responded so much, wife noticed. Used it in my '88 and it lowered MPG by a bit. Last few yrs, I winterized the 20w50 by adding a pint to the oil, Car started fine. So I did for the last few yrs I had it on the road. grin2
*OPE is a good application for MMO nowadays - otherwise in modern vehicles top tier gas and a bottle of Techron in the gas tank before every oil change is good enough .
 
Messages
6
Location
MA
Used it with an old lawn tractor after we forgot to do an oil change. Drained the old oil, filled it back up with Marvel, ran the engine for an hour or so. Lots of gunk came out. Never tried it in gas though.
 
Messages
1,408
Location
Gone Fishing
Originally Posted by Dragon44
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.
not every other tank i really think this is counter productive to fuel efficiency, although its hard to prove. it's along the lines of affecting the flame front in my opinion. i subscribe to the add a good pea cleaner prior to your oil change. right now i'm doing 5k mile oil changes so a tank or two before it's due for oil change, i add a bottle of pea based cleaner. run the tank then change motor oil and filter.
 
Messages
66
Location
Washington
The only time I use that in my vehicles is when I get a used vehicle. I run new to me rig for a bit to see how it works, add some to fuel and oil, run it for 500 miles and change the oil. I don't know if does anything but it has detergents so hopefully cleans something.
I use it religiously in my small equipment. I get 2oz per 5 gal can and then also add 1oz extra per 1 gallon to my 2 stroke mix fuel (plus 3.2oz of what ever two stroke oil in using). When I get new-to-me small equipment I warm it up and then put MMO straight on to the cylinder and let it sit for 24+ hours and then starts it. Noticeably cleans the piston.
 
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