For what it's worth, a friend of my son's is a tech (mechanic) at a local RV dealer.

Long story short, customer purchased a used class B motorhome. Motorhome is a 1996 model and has had three fuel pumps replaced since then! Customer (owner) was fed up replacing them, as it's relatively expensive, (parts + labor) but most of all, when the fuel pump quits, you're stuck.

He was told to try using a quart of Marvel Mystery Oil when he filled the tank. He purchased a case, wholesale, and did just that, and no more fuel pump failures! Thinking is, MMO gives just enough of a top lubricant, and helps keep the pump cool along with the gasoline. When the other pumps had failed at or around 23,000-25,000 miles, with MMO and almost 40K miles, fuel pump is working as normal.

The customer had returned to the dealer for some basic maintenence after attending the recent NASCAR race at Infineon Raceway, Sonoma, CA here in northern California. Told the story to my son's friend at the dealership, and my son was telling me this on Saturday.

I know we've discussed MMO on occassion, whether it works or not, I thought I would pass this along to the board.

Ed

 

been a believer in the stuff since the '60's
it keeps the fuel system lubricated and the top end lubricated and helps to clean carbon from the valve stems (always add with an oil change too)

 

Good stuff IMO. I use Lucas in my gas tanks, more money but it really lubes the pumps. Not a surprise to me.

 

I like Marvels Mystery oil, had a dead cylinder on my ranger with about 70 lbs of compression, put in some MMO, and within 20 minutes it was back upto 160 lbs. Free'd up the rings I think.

 

Known for reducing valve wear/sticking on iron barrel Harley Sportsters too. Good stuff.

 

Somewhere on the 'net (so it MUST be true ) I was reading that MMO is just a blend of ATF and kerosene. Dunno if that's true or not, but I've been using it forever, because my Dad told me to when I was a kid. Smells neat, too... I get it by the gallon at Wally's and put some in everything's tank.

 

Why not just use ATF. My old boss in Palmdale had a GM diesel pickup that was eating up injection pumps. He started adding a pint of ATF per tankful, no more pump replacements. Yes, its the lubricity. Downsides of mixing any type of oil with gasoline in a modern fuel injected, emission controlled engine? Possible coating of the O2 sensor with ash, long-term damage to the cat converter, and oil mixing tends to reduce octane rating of the fuel, so you may lose a little efficiency or have to go to mid grade, an extra expense.

Jim

 

Marvels mystery oil was first made in 1923, the first mass produced automatic was made in 1940s. So I doubt that is what marvels mystery oil is

Octane is not how much energy the gas has, its how resistant it is to detonation. Adding oil to gas would actually increase the octane.

 

I use MMO in my 74' F-100 for years. Has been ran hard with the MMO and still runs great. MMO also acts as a fuel stabilizer. I will continue to use it on my 74' but as for my 04' SD I don't use any additives. I did notice a while back when I was using a LOT of MMO in my 74' it turned the ceramic on the spark plugs a reddish color.

 

Exactly, but gasoline-oil mixes are less resistant to pre-ignition and detonation than the same gasoline alone.

Jim

 

Hmmm, I've always used Lucas Upper Cylinder Lubricant, I wonder how MMO and LUCL compares. I'd say they both do nothing but good.

 

The MMO added to gasoline, in a small ratio should not do any harm to the cats and O2 sensor. In fact the gasoline will dilute it so it's not as though it's pure MMO being burned via combustion.

 

MMO recipe, minus the winter green oil part & some others as well.
Ford Truck Enthusiasts Forums - View Single Post - Marvel Mystery Oil experience

 

I just started using mmo last yr when my truck was knocking pretty bad put a quart in my oil and no more knock but I also put in 15w-40 rottella t in my 460

 

As for reference, my original fuel pump lasted for about 150k. The replacement has almost 70k on it, and no, I didn't use any additive.

I did a post mortem on the failed pump, and it was an end of life wear out. (the commutator was partly gone)