Given tar is a hydrocarbon, anything completely water based will have little effectiveness. Simple Green should work on tar, try it nicely diluted first.A pointabout Simple Green is it is highly alkaline (acidic), so wherever you use it, you want to make sure it is THOROUGHLY rinsed off. If you leave SG on there, the acid will continue ... being acid.

WhatI like about simple green versus the claybar ... with the clay bar, you are using friction. The bar itself may be non abrasive, but you are rubbing. There is some friction at play, you are forcing/pulling the tar off. With SG, you are chemically disintegrating the tar, changing the tar molecularlyso it releases, then rinsing, the process is completely non abrasive. As long as you have confidence the SG will not damage the paint finish (diluted in accordance with the instructions, then rinsed thoroughly within a short time frame, it should not), it seems a better path to me.