Thank you for your answers.
We run an IR of the contaminated sample, and clean products, there was some coincidences, singinifacatrives, as a matter of fact around 2900 cm-1 and 1000 cm-1, there was some peaks that help me to say, that in very general terms, the contaminated sample, had been in contact with the other lube. I repeat, based on the peaks coincidence of the contaminated sample and the clean samples.
Rudimentary but effective i think.
Thank you for your support. I will check the metallographic analysis to confirm.