I stored a running engine for several years, but unfortunately I didn't consider very carefully how I did so. I dowsed the engine in Marvel Mystery oil... snake oil. What a mistake! It dried out and turned into a caramel like goopy to hard coating and completely seized the engine! I used WD-40 to loosen it up some and painstakingly disassembled the engine bit by bit. Needless to say, I won't be using Marvel Mystery oil for anything anymore.

I bought my first bottle of MMO last fall but have not used it yet. (I had some of the Hobbico after run oil left). I hope there may be something else that contributed to this "gumming up" of the MMO.
There are a LOT of guys that use this all the time for AFTER RUN OIL. Have any other of you had the same problem???

Sparkey,
I use Marvel Mystery Oil after each flight regardless of how long between runs and have never experienced any gumming as you described. I've had engines stored as long as 2 years with no problems. I understand the MMO made for air-tools works the best. I've not tried it yet, however, as soon as my current supply of MMO is gone, I will.
BTW. How much fuel did your "stored running engine" consume over those several years. (sorry, couldn't help myself)

ED

I have used Marvel Mystery oil for many years including storing engines for long periods with no tendency to gum up. I recently took out and used a couple of old ROSSI's that had been stored close to 10 years... they were like new. I always store my engines in a large, sealed, freezer bag and lightly coat the outside/inside with MMO and wrap a rag or paper towels arround the engine. Could it be there was still some fuel in the engine when it was put away? I have recently switched to air tool oil because it has been proven to my satisfaction that it is even better than standard MMO.

I have stored engines, and still do for many years with MMO and never experienced any gumming.

Vince

have been using MMO for over 20 years
56 engines in display case every 2-3 years reoil and turn them over also run most of then once in a while never had this gumming with MMO some engines I got were realy bad but a soak in glow fuel for a couple of days in a sealed jar and then dismantle and oil with MMO get's them real nice

Hi Sparky,RAN ACROSS THIS PROBLEM COUPLE YEARS BACK,SOAKED THE ENGINE IN ACETONE ,FLUSHED IT WITH PAINT THINNER,PUT SOME TRANSMISSION FLUID IN FOR THE BEARINGS AND WENT FLYING,TOOK COUPLE DAYS OF SOAKING TO CLEAR EVERY THING UP.MINE HAD AFTER RUN OIL FROM THE LHS,SWITCHED TO AIR TOOL OIL.

When I store mine, I Make some kind of plate to cover the exaust outlet, use mmo and fill the engine up till the oil comes out of every orofice, then use the trusty 'ole food saver to vacuum seal them. Then when I get a plane or whatever the case may be, just cut open the bag, dump the oil out, give it a good nitro bath, then on the plane it goes. No problems yet. You can also put rice in the corner of the bag to soak up moisture, if any happens to form.

I had a engine stored in a zip-lock plastic bag soaked in MMO for almost 10 years

...unpacked it last spring.... was just like I had packed it away...turned over fine... no gumming, no visible rust.... Engine has been working great so far...