Scrubbing Away

This was a hard one, but the soap I have would wash away the damage done to old car parts, restoring them to a new condition.  Driving an old truck, you end up having to replace parts that are just worn out in order for your truck to keep running.  And it can take a big chunk out of your savings if you aren't paying attention to the warning signs that something is about to fail.  A soap that could magically wash away that damage would be a great relief to my checkbook.  Although, it would mean that I  would probably need to take a beginners mechanics course so I would have an idea on what the parts should and shouldn't look like.

(Writin prompt 290 out of 300: You have a magic. What does it wash away?)