I use S100 engine cleaner, followed by S100 Engine Brite. The cleaner is really only marginally better than a very good wash, but the Engine Brite makes the black look like it just came off the showroom. And it stays nice looking for a year or better. Engine Brite comes out of the can in such a fine mist, it looks like smoke. Every couple of years, I wrap some 320 grit sandpaper around a flat stick and hit the edges of the fins to brighten them up.