Marvel Mystery Oil Feedback

The most important thing you should know about MMO is that it is an EXCELLENT detergent. It can clean fuel systems very well, sometimes TOO WELL. I know personally of several people who used it in marine fuel tanks - yes, I was one of them!

It removed every bit of grunge in the tanks. Good right? Well, yeah, except for the problem that all that grunge had to go somewhere. It caused the fuel filters to completely clog in 20 minutes and continued doing it for 5 filter changes. I finally had to "vacuum" the fuel tanks using a fuel pump, a wand/hose and a large Gulf Coast F1 fuel filter (weighs 40 lbs). Luckily, since there were 2 tanks and they were each half full I was able to transfer the fuel back and forth as I vacuumed the tanks. Took two days.

MMO is not snake oil like products such as STP, etc. In fact, it used to have a Milspec number and was extensively used in military vehicles. It will unseize engines and I have also seen that done and done it myself several times. It is very commonly used by aviation folks and you will find lots of good info about it.

But I would not put it in a fuel tank unless you are prepared to replace a lot of fuel filters or you are prepared to drain all the fuel from the tank if necessary. Obviously, if the tank/system is not "dirty" to any great extent, there won't be a problem but you probably won't know that until you use it.

I think MMO is great stuff but I do not routinely put it in any vehicle though I have used it a lot for specific issues over the years. It is also quite a good penetrating lube - at least as good as the high dollar products like Kroil, Break-Free, etc, etc,etc.

Frankly, I would view it in the sense of "what's wrong that you think it might be useful." If nothing is wrong and you wish to use it as a cleaner or whatever, understand that it might clean too well!

 

I'm not sure why you would need MMO in a 3X8. Pre War Classics often use MMO oiling systems that inject a single drop every so often to improve lubrication. (My father's '29 Franklin has such a system.) The oiling system in F-cars are more than adequate for top and bottom ends, and the fuel system has ample filtration.

 

yes, 5 308, (4 carb and one injected). used it in the oil. in the fuel i prefer Seafoam, but i have esed MMO in the gas on some of the early 308s i had. if your fuel tanks have that much crap in them that the filters keep clogging, then they need to be pulled and properly cleaned. no magic in a bottle will fix them if they are that bad.

 

I haven't used it in my 308, however my MB had a squeaky water pump and I added about a tbsp to the cooling system. The noise went away after the first drive. No issues since and the running temp is perfect. That was two seasons ago and the noise hasn't come back.

 

I have not used MMO, but I had an odor problem with my 78 carb 308GTS when I would pull into the garage and shut it off. Switched from the cheap gas to Shell, no improvement. Switched to Chevron, big improvement. Still a little odor bit not much. Randy

 

You can use it on airplane engines too!! Works wonders on an old Continental.