I've been trying different chemicals on my original anodized S4 flats. I tried some wheel cleaners, some home remedies, and several soaps. (I have not tried the expensive German cleaners from Griot's Garage or other mail order houses.)
The results are surprising. The best "clean" results from a liberal application of Goop hand cleaner followed by the factory-recommended Vaseline. The Goop removes all the brake dust and embedded road grime. The Vaseline (petroleum jelly) returns the factory sheen. Be sure to wash and copletely dry the wheel before you start with the Goop. (It is water-soluble.) Rub the Goop in with a heavy towel or sponge. Then rinse off the Goop. When the wheel is again dry, rub in the Vaseline with a heavy towel. Finally, polish the wheel with a clean, dry towel. The down side is that it takes about 2 hours for 4 wheels.
The cleaned wheels look very different from polished, plated,clearcoated or painted wheels seen on more common cars. I still prefer the aftermarket or reproduction "cup" style wheels, but if you cannot afford new, at least your old wheels can look new. It's much better than the dirty gray look frequently seen on old 928 wheels.
Now you have something to do this weekend,
87 S4 5sp, red/black, 48k, Aiken, SC
I also tried factory recomended applique of vaseline- use care! I found a great deal of difficult to remove gummed up brake dust and road spoils after several thousand miles (with routine washings every week or so). YMMV
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