[Werner]

Chris, I meant an oil filter. The only way to take away the dirt out of the filter-less enginge is to change the oil.

Woofa Express, maybe a misunderstanding? Also aviation engine oil is slightly alloyed. Old Lycoming etc. may not use heavily alloyed HD oil due to combustion residues. But even a lightly alloyed engine oil gets dark in 100 ml.

I worked in the oil industry. If you tell me the exact oil name you've filled in, I can probably say more.