What determines the impurity of one thing over another, and what is the ruling on newly introduced substances such as car oils, and is it permissible to pray with them or in work clothes?

Allah Almighty permits and prohibits for the benefit of humanity. He permits only what is good and prohibits only what is evil. Prohibited things are either harmful or considered vile. The classification of things into pure (ṭāhir) and impure (najis) is not man-made. Jurists have detailed what is pure and what is impure in the chapter on ritual purity (ṭahārah). Impurities include human urine, flowing blood, carrion (except for marine animals and locusts), pork, the urine and dung of animals whose meat is not permissible to eat, and intoxicants (khamr). As for inanimate objects, plants, and oils, they are pure, and prayer is valid while being in contact with them. It is desirable for a Muslim to be clean when praying, and their prayer is valid even if they wear clean work clothes and cannot change them.