You might wanna try some simple green... I used a blend of about 50% simple green and 50% water, mixed into a windex bottle, and i actually used it on my cars engine bay, and you just spray it all on, let it sit for 5 or 10 minutes then power wash it... My engine bay looked showroom after that, and the intake manifold was as shiny as tin-foil... My friend said it works so well because it has some acidic properties that only react slightly with aluminum, so in essence it's actually like power washing the dirty layer of molecules off your aluminum parts...