I'm looking into getting an alloy cleaner for my monza's too and after reading into different products have decided to go for R222 gel wheel cleaner, it's got good reviews and is PH neutral so won't damage the alloys at all, plus for heavy soiling u can leave it on for up to 2 hours giving the gel time to loosen everything up. Unfort I have just ordered so can't give u a first hand user comment. But worth a look. .....