I've seen what the wrong degreaser does to magnesium in an M112. What's safe to use to clean things before chasing valve cover area leaks?

Thanks,
Sixto
83 300SD
98 E320 wagon

mean green and a parts brush then a wash away with water. Dont use anything too caustic on it.

or for just the valve covers a can of cheap brake cleaner spray.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)