Ring Flush

[EricJ]

4 hours ago, Yetti said:

I am not saying that MMO will help you make a stuck valve get to annual, but if you think about it the engine design and MMO are of the same vintage.   

MMO dates back to 1923 as a carburetor cleaner/flush.   Word is that radial engine maintenance outfits in WWII got it by the barrel, and used it up regularly.   It's been a regular component in aviation maintenance for nearly 100 years.   Not even remotely a new or untested thing.   

[carusoam]

How would one know…

The oil ring is a bit gummy?

 

Then…

How would one know…

The oil ring has been cleaned?

 

Sounds like…

Oil may be showing up in the lower spark plug?

A sign that the oil ring isn’t doing its job…

could be a cylinder surface quality issue as well…

 

If sending a camera down the cylinder is possible…

be on the lookout for polished surfaces where they used to be cross hatchings.

 

+1 for selecting a solvent mix that is good at dissolving carbon…

 

PP questions only, not a mechanic…

Best regards,

-a-

[M20E for me]

Mikes recipe calls for Xylene which is no longer available in California, anybody know of a good replacement?  Googling a replacement I get Polychem 36 but can’t seem to find a source, haven’t called the manufacturer of Polychem yet.  Might just use MMO.

[N201MKTurbo]

1 hour ago, M20E for me said:

Mikes recipe calls for Xylene which is no longer available in California, anybody know of a good replacement?  Googling a replacement I get Polychem 36 but can’t seem to find a source, haven’t called the manufacturer of Polychem yet.  Might just use MMO.

Goof off is mostly xylene.

[PT20J]

1 hour ago, M20E for me said:

Mikes recipe calls for Xylene which is no longer available in California, anybody know of a good replacement?  Googling a replacement I get Polychem 36 but can’t seem to find a source, haven’t called the manufacturer of Polychem yet.  Might just use MMO.

I know an IA who tells me he has successfully used MMO to flush stuck piston rings. MMO contains TCP (lead scavenger), o-Dichlorobenzene (dissolves carbon), p-Dichlorobenzene (solvent) in mineral spirits. Plus the wintergreen oil makes it smell good 

https://cdn.shopify.com/s/files/1/0055/5922/2385/files/MM12R_50094_MM13R_50095_MM13RC_Marvel_Mystery_Oil_SDS_US_031424_FINAL.pdf?v=1733406643

[M20E for me]

23 hours ago, PT20J said:

I know an IA who tells me he has successfully used MMO to flush stuck piston rings. MMO contains TCP (lead scavenger), o-Dichlorobenzene (dissolves carbon), p-Dichlorobenzene (solvent) in mineral spirits. Plus the wintergreen oil makes it smell good 

https://cdn.shopify.com/s/files/1/0055/5922/2385/files/MM12R_50094_MM13R_50095_MM13RC_Marvel_Mystery_Oil_SDS_US_031424_FINAL.pdf?v=1733406643

Thanks, it will be the easiest way to go as well! 

[PT20J]

I always thought the mint odor of MMO was a gimmick. But, it turns out that methyl salicylate (aka oil of wintergreen) has a known beneficial effect on rubber seals.

[CL605]

On 2/2/2026 at 1:44 PM, PT20J said:

I always thought the mint odor of MMO was a gimmick. But, it turns out that methyl salicylate (aka oil of wintergreen) has a known beneficial effect on rubber seals.

I previously had a Sundowner to teach my kids to fly. It used the same style rubber donuts as the Mooney. Beech wanted $5000 for a full set. Before sourcing them from South Africa for $800 for the set I tried wintergreen oil. It definitely helped the old donuts. They regained elasticity and swelled up to almost new size. I just replaced the donuts on my J and I’m tempted to give them an occasional coating of wintergreen oil. It works.