Big Lots has these each for $3.50 and I picked up a bottle of each. Are they safe to use - I have chrome wheels on my vette and I think my wife's Lexus has painted wheels. The Multi Piece Wheel Wash says it's pH-safe, but the Gold Class Instant Wheel Cleaner says it contains Ammonium bifluoride. Since I never took a chemistry class, I need your help so I don't melt my wheels. lol.