Organic contamination and tar residue can be found on any type of vehicle due to their usage. To remove safely this type of contamination you can use Q2M Tar. 

Spray Q2M Tar liberally on a clean and damp vehicle. Use it locally on contaminated area. Let dwell, but do not allow to dry. The solution will react with the contaminant and turn brown. Rinse off heavily, inspect  & re-apply if necessary.