I got into a little spat with one of the OPT reps on the OPT forum about doing headlight prep with IPA, they said I should be using the OPT paint prep, that IPA leaves residue, so I got all bent and went and looked at the SDS, and the OPT prep spray actually does NOT have IPA in it (I thought).
I just went back and looked, and it's 1-10% 2-propanol (which IS IPA), and 1-10% n-propanol, which is an isomer of IPA. (I guess I'd better go back to the OPT forum and ask them to explain why their prep is better than IPA when it has IPA in it). But of course the bottom line is it's 80-98% WATER, no fragrance, no lube (talking about the OPT prep)...hard to stomach paying $36/gallon for mostly water.