This was in my mother's 3.1 liter Lumina; my Dad put some "Marvel Mystery Oil" in it to try to loosen up a lifter that was seized when the engine was cold. Three weeks later it had to be towed home. The motor was seized up bad enough that the starter wouldn't turn it. We took it apart today and the oil was somewhere between jelly and chocolate syrup. When we pulled the drain plug we had to punch a screw driver around in the pan to get any of it to come out. It still has the drain plug out with the last three quarts or so sitting in the pan and engine.
The motor is killed. The day it broke down was the coldest we've had here yet, we suppose it was just cold enough to raise the viscosity so the pump just couldn't pump it. We turned the crank with a wrench and heard stuff dropping into the pan and scraping. Don't know of any warnings on the bottle about how not to use it, can't find much on the web, the official site doesn't work. My Dad has been a mechanic for about 30 years said he's never seen an additive do anything like that to oil. It was a 180k mile engine with the "max life" Valvoline in it, supposedly good for high mileage engines. Maybe something in that oil didn't like the Mystery oil.
Does anyone know anything about this?

 

Thats why I don't use any of those "miracle in a can" products. They are usually just band-aids to a bigger problem anyhow. Are you sure there wasn't a head gasket leak? Coolant mixing with the engine oil could also create what you are describing.

 

That's a good suggestion but there's no coolant in the oil. If there were the motor oil would be whitish grey looking and foamy. This stuff is all black.

 

I think that anything in the oil is engine bearing suicide. Oil is the blood of the engine.

 

Sorry to here it. I just got over changing the lube on my Lumina with the 3.1also (Winter driver). I was thinking of trying an oil treatment but had a bad feeling and chose not to. Now I'm glad I didn't use it.

 

I actually used Marvel Mystery Oil for a long time. Never had any problems. It's mainly just a solvent to help clean the engine out. Highly doubtful it would cause what you experienced. How long had you owned the car? was the oil changed regularly? possible it just broke loose all the crap that had been hiding in the engine and the pump sucked it up.

 

i wouldnt run marvel for any more time than about 10 minutes...if that...and only if i knew i had to rebuild the engine any way.

 

MMO is a good product, far from snake oil... I highly doubt it caused your problem..
if anything it would thin the oil..
Like mentioned it may have freed up some gunk that was in it for years..
I have used it for many[35+?] years with no probs whatsoever.. in all types of engines..
It's especially good for 'before they used hardened valve seat' older motors as a lead substitute, old Harleys etc..[add to gas for that..]
I am not a big fan of the usual additives, but this is one that's worthy..
I wouldn't put it in a motor that wasn't already very clean inside tho FWIW..

 

Diddo.....

 

3.1s are notorius for having coolant leak into the engine
greg

 

I put MMO in my vehicle. No problem to date.

 

If the MMO was put in to "loosen up a lifter", then it was obvious it was thought to have some solvent properties. It's more likely that it also loosened up a lot of stuck-on sludge that was already in the engine and that clogged it up.

 

My experience on 180,000+ mile vehicles is to do as little as possible. Everytime i try to have it do more than change the oil and top of the fluids i end up with a major problem. I won't even wipe the grease off of anything.

 

any pics?

 

Your problem was not caused by MMO.
Have used it from the '60's with no problems. Follow the directions on the can.