501 is marketed for marine use but many folks, like me, have been using it for years on their cars. It absolutely will not harm paint. It's a much better cleaner, IMO, than 105 (which I find to have nearly no cleaning ability) but I often layer the 501 with 105 because I think 105 leaves a better appearance. Of course, I just about always top the 105 with 845, so....At any rate I highly recommend 501.