3m All Purpose Cleaner is great for removing tar off your car's paint and it won't hurt it either. I also tried it on a small dirty spot on one of my aluminum rims that I couldn't get off with washing and it took that spot right off with no harm done to the rim. This is the way I do it:

1. Fold small terry cloth and then cover opening of the 3M cleaner can with the folded towel and then gently tip the can over to get a small dab of cleaner on the towel.

2. Lightly and gently rub over the tar or spot with the dabbed part of the terry cloth and the tar will come right off.

I use the same procedure for my rims.