Its powder coated, you can use any non abrasive cleaner. I use 409 cleaner and it does a good job. If it is on the stainless try mothers metal polish, also works great on board racks.
Greg, I have tried a few things on my '10 LSVs G3 and not much works on it to cover stains. I have some weird blue stains on the black that almost look like a paint pen made them and was wiped off at the factory. If you scratch or ding the black powder coating the best thing I have found to fix it is Rustoleum truck bed liner spray. It has the same texture and color as the black coating on the tower and is really durable being truck bed liner. I spray it in a plastic lid of some sort and daub it on with a Q tip. It also works great on the sun deck supports bars under the rear deck lids. When it dries I go over all of the black on the tower with 303 which blends it in and helps to keep the black from graying out from UV damage. LikeTravis I also use Mothers on the SS and the board racks.