I have one and have used multiple solutions in it, like Purple Power, Some sort of Aluminum Brightener Cleaning solution (forgot the name) and Simple Green concentrate. It seems any good degreaser will work about the same as the other. Simple Green does work and it is fairly cheap...
BUT, the heat seems to make the biggest difference and so when you use it, crank the heat up and make sure it is hot when you want to clean your parts.......
Just my .02.....YMMV....grr