Wonder if purple power is the same or a new name for Castrol Super Clean?
The Castrol is purple and comes in a purple container, seems like a name like purple power would sort of infringe on what Castrol has going already.
The Super Clean used to damage aluminum but now it says "new formula, safe for aluminum" on the label.

 

Different techniques depending on the nasty. My preferred & regular technique that works on most of the nasty is high pressure air with a long nozzle gun. A rag in all cases + a small brush.

Oil & grease requires Purple Power or Simple Green + a water hose (which I have hardly ever needed to use).