I just changed my oil 200 miles ago.  My #4 cylinder is indicating a misfire, and I’ve come to the conclusion (for now) that it may be a stuck valve on that cylinder, since the compression is reading 90 lbs., and the cylinders on either side are reading 180 lbs.  What I want to know is if I can add 4-5 oz. of MMO to my crankcase in lieu of adding 20% with my next oil change.  Will this do more harm than good?  I’m not low on oil at this time, and I definitely don’t want to overfill the system, but I want to try this… ideas?

I would add 8 ounces. Being a half of a pint over filled won’t cause any harm unless its a very small crankcase. I assume that you have at least a 4 quart capacity.

Yes, I have a 6 qt. capacity.  I assume that I need to drive it for a while before I notice any improvement.  I just added about 4-6 oz. a few minutes ago, and revved the engine to around 3000 rpm for five minutes or so.  So far nothing is changing, but I have high hopes.

With a 6 quart capacity, I would add 16 ounces and drive it like normal for a week or two. Good luck.

ajeepthang73 - 08 July 2010 04:03 PM

I just changed my oil 200 miles ago.  My #4 cylinder is indicating a misfire, and I’ve come to the conclusion (for now) that it may be a stuck valve on that cylinder, since the compression is reading 90 lbs., and the cylinders on either side are reading 180 lbs.  What I want to know is if I can add 4-5 oz. of MMO to my crankcase in lieu of adding 20% with my next oil change.  Will this do more harm than good?  I’m not low on oil at this time, and I definitely don’t want to overfill the system, but I want to try this… ideas?

MMO is a slow cleaner, using such a small amount isn’t going to do much of anything.  If you are trying to free up a stuck valve I’d use the suggested amount of MMO and go the distance with it.  Or use at least a pint, and run it for the full OCI.  It won’t do any harm that’s for sure.

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Try adding an ounce or so to the intake and fuel supply. Directly to the intake will cause some smoking for awhile but will get to the valves quicker than from the oil sump.