Been using Simple Green on the OEM wheels on my 2005 E320 CDI. There is a scary link talking about hydrogen embrittlement on certain alloys. Does anyone know if Simple Green is okay to use on the wheels? Thanks.

Simple Green is corrosive and will react with bare aluminium causing hydrogen embrittlement (used on suspension components).

Here's their FAQ...

Simple Green products have been successfully and safely used on aircraft, automotive, industrial and consumer aluminum items for over 20 years. However, caution and common sense must be used: Aluminium is a soft metal that easily corrodes with unprotected exposure to water. The aqueous-base and alkalinity of Simple Green or Crystal Simple Green can accelerate the corrosion process. Therefore, contact times of All-Purpose Simple Green and Crystal Simple Green with unprotected or unpainted aluminium surfaces should be kept as brief as the job will allow - never for more than 10 minutes . Large cleaning jobs should be conducted in smaller-area stages to achieve lower contact time. Rinsing after cleaning should always be extremely thorough - paying special attention to flush out cracks and crevices to remove all Simple Green/Crystal Simple Green residues. Unfinished, uncoated or unpainted aluminium cleaned with Simple Green products should receive some sort of protectant after cleaning to prevent oxidation.
JonM

When you wash your car.......use a seperate terry rag to wash your wheels with the same soap your using to shampoo the car......If you need caustic chemicals to clean the car...you are not washing it enough......

Less is more and more is too much