The air had a slight smell of machine oil.

But a drop of machine oil in every cup?

Maybe some dust, and the faint trace of machine oil or something.

The two of them were filthy with machine oil.

It was done with a sharp pencil and machine oil.

A machine oil stain could also contain traces of metal, for example.

The air was humid, hot, with a smell of machine oil and sweat.

Then he straightened up to hunt for some machine oil.

Will felt as if he'd bathed in machine oil.

He rubbed a moist palm across his mouth and smelled machine oil.