Originally Posted by semtex

I just spoke to my mechanic. He said it might actually be brass you're seeing, not copper. So what's brass used for in engines? He said it's typically used in bearings and valve guides. I'd take this with a grain of salt though. I asked him what copper would be used for and he couldn't think of anything. But clearly, there's copper in engines because Blackstone tests for it. And the don't test for brass. So, I don't know how solid what he told me is.