What is "grit" on oil filter microscopy?

[DXB]

So - I'm not big on oil analysis (a rant for another thread) but I'm dutiful in cutting out and carefully examining my filter element every time and scoping my cylinders ~50 hours.  It's an O360-A1D with 22 years and ~1430 hrs SMOH, flown >100hrs/year in the last 7 years since I became owner. I run Phillips XC 20/50 with Camguard year round.  After a previous oil change at 45 hours, I saw a few tiny silver flakes (maybe 5-10) that didn't stick to a magnet and were rock hard to the touch.  I wasn't too concerned.  I recently did the next oil change after 33 hours - I saw maybe 30-50 very similar looking flakes (tiny, silver, nonferrous, rock hard) and got more perturbed.  I figured I had a broken ring or piston pin cap issue maybe.  I sent the filter for electron microscopy at AvLabs and was surprised to get back this reassuring sounding report. But what is "major grit" in this context??  

Only change I've made is that I've added 1 quart of MMO to my oil 1 hr or so before my last two changes.  I wonder if the solvent has shaken loose some sludge but but I wouldn't expect 50 rock hard particles to make it into the filter. 

 

[A64Pilot]

I’d have to call and ask myself, Military SOAP dirt (sand) came in as silicon,don’t know what grit means, perhaps particle size?

MMO seems to work in a similar manner as ATF, that is ATF has a high detergent content and will help clean up whatever, fuel injectors in a Diesel for instance, MMO seems  also to do the same, so yes I think if there were sludge it certainly could break it up and the filter catch it.

Small non ferrous metal, I’d suspect a wrist pin plug myself. I believe you can verify it’s aluminum with pool acid diluted somewhat, Muratic acid is cheap hydrochloric  and aluminum will react to it and be eaten away and give off hydrogen gas, dirt and carbon etc won’t react.

[philiplane]

Hard particles are often lead bits from the combustion process that have made it into the oil. Aluminum slivers are distinct shavings, usually coming from the piston pin plugs due to corrosion pits on the cylinder walls. Those will often go away on their own as the engine runs more, and the bores polish smooth again. 

We can't have unleaded fuels fast enough. Most of these problems will go away once the lead goes away. Lead causes all kinds of problems inside the engine.

Edited February 4, 2022 by philiplane

[A64Pilot]

Just thinking it could even be an accy, like a prop governor?

[carusoam]

Dev,

Got any pics to go with that?

Maybe next time…

My O360 only sent a few particles of aluminum to the oil screen during my decade of ownership…

Random pieces carved off the inside of the engine… nice and shiny all around…

Never looked into the bottom of the engine… there could have been a lot of things sitting in a sludge pile we never thought about…

 

Best regards,

-a-