Originally Posted by
smoothness
i'd say go easy on the harsher stuff, and stick to a magic eraser/soap and water/vinegar. when i was cleaning some old gran compe and shimano hoods, i just used super diluted simple green, a magic eraser, and ten minutes.
i'm sure there's a chemist somewhere here who'll probably tell you the stronger chemicals could actually make your situation worse, whether it be oxidation or actually melting the material.
+1
Start with the least harsh chemicals such as diluted dish detergent (Dawn works really well at removing grease and not leaving a film), and/or vinegar and a Mr. Clean magic eraser. Go to diluted Simple Green if there's lots of grease and something like Dawn isn't getting it out. For plastic/rubber hoods a tooth brush and a baking soda solution may also work for you, I wouldn't use it on leather.
Keep in mind that if the surface you are cleaning is porous it's going to absorb some of whatever you put on there, then leach it out over time onto your skin/clothes, you don't want anything harsh doing that.