Those of you who use Marvel Mystery Oil (MMO) in their engine during oil changes, how much do you add? A qt, half a qt? I have been using MMO in my fuel for the VE pump (to help with the new ULSD), and figured I would try it when I change oil as well. Is this adviseble or a waste of time? Some old timers' swear by MMO in their crankcase

 

Other old timers swear by ATF in the tank, too. Just cause it worked a long time ago means nothing today. BTW- not bashing MMO, I just think it sounds too good to be true, so I steer shy of it.

 

I like MMO in the fuel but not in the crankcase. It is just going to thin out your oil. That is the only reason I could think of to use it in the crankcase. Maybe you live in a real cold winter area and didn't put much mileage on your 15w40 this summer and trying to stretch it till Christmas? Best to just use the right oil in the first place.

There are better products out there for cleaning the insides of the engine, if that is what you're looking for. AutoRX is the best. Those harsh kerosene-type flushes will do some cleaning, but are dangerous.

Waste of time and potential excessive engine wear.

 

Ace, Thanks for the words of warning - regarding using MMO in the crankcase. I will stick to Rotilla 15/40 in summer, and 5/40 in the winter.

 

STP contains MoS2 - moly - which is good for sleeve bearings, piston skirts, timing gears, camshaft lobes, rocker arms, etc, ect - all things frictional or subjected to heavy mechanical loading.

Add 8oz STP per oil change - your engine will love you for it...............

 

This isn't a diesel story, but a friend of mine was having a loud tapping noise coming from one of his big block boat engines on a trip down the "ditch". We stop in NC and put a quart of MMo in the crankcase and after about an hour of running the lifter loosened up and the noise went away. Could be coincidence, or................?

I don't believe in a mechanic in a can, but sometimes a little extra something doesn't hurt.

 

MMO will do that, but the real question is how long do you want to run that while it's doing who knows what to the rest of the engine? I like STP too, at least where a heavier oil is beneficial like in these diesels.

 

Not too technical (mainly because I'm just reaching), but if used in a diesel it would dilute the oil additives that keep the soot flowing instead of settling. On a gasser, you don't have the soot in there & wouldn't have any issues using it. I've used it on mowers & have noticed them to run a little smoother.

 

MMO contains extra detergents, very good for hydraulic lifters - can clean them right out, restore proper pumping action.

However - your Cummins engine has flat-tappet solid lifters - looks like an upside-down nail, head down, shank up.

Not much use for MMO lifter-detergent in a solid piece of steel, not much use for MMO in your engine - or your fuel tank

Go with STP, or any crankcase additive with increased ZDP - reduces friction.

Go with two-stroke motor oil in in your fuel tank - it's just a lubricity improver, reduced friction in the IP plunger\barrels.

Try it - you'll like it..........