I use WD40 on a regular basis for cleaning my aluminum intakes, it has never failed me! Medium bristle brush (toothbrush type), WD40 and then a bit if brake cleaner to remove any remaining residue. Good luck!

for an as cast look used to use alumibrite it is a mild foming acid works wonders used to work at a truck wash an cleaned tanks steps and livestock trailers to good as new just dont let it site too long

I use that stuff for cleaning a/c coils....does a nice job :wink: