Anybody use Marvel Mystery Oil??
 

I'm wondering if this is harmful on the fuel injectors. I want to run a bottle of fuel injector cleaner then MMO. I've heard alot of good things about it.

I credit MMO for saving my Sonoma's 4.3. This was awhile back, but my wife had taken it to work one day, and on the way home (15 mile trip) she said the oil pressure gauge went all the way down(no pressure). She said it sounded normal, so she drove it all the way home and put it in the garage. These vehicles have the off-motor filter setup, and the gasket for the feed line connection to the motor gave, so it had pumped all the oil out of the engine. Put new gaskets in, filled oil, and started right up. Still running today.

Did you have the MMO in the gas tank or the crankcase? I know you can use it for both. I would be real hesitant of putting it into my oil.

crankcase

IMO it is a good product. I've used it in my cars for years. I'm running a can in my '95 Vette now to clean the lifters a little. Crankcase only for me. Haven't tried it for injectors. May work, but I use injector cleaner for that.

Do you recommend against always having it in your crankcase? I just added it into mine but won't be getting another oil change for probably another 3,000 miles/5 months..

I don't believe you will experience anything adverse. Just to be on the safe side I'd change the oil and filter around 3K miles.