I just used Bounce fabric softener moistened with water to remove stuck tar and dried bugs from my car. It worked like a charm, wiping it clean in seconds. Why did this work? The web says it contains dipalmethyl hydroxyethylammoinum methosulfate, among other chemicals.
Water is the universal solvent. But it doesn't do a great job dissolving road tar (i.e., asphalt), or bugs. Wiping is an important part of removing dirt from a hard surface - in addition to obtaining a lower surface tension so the surfactant solution can actually wet the dirt, and the surface.
In many washing applications (like dishes or laundry), nonionic or anionic surfactants are used to emulsify oils and suspend them in the wash water or foam. The low surface tension of the solution is the major actor.
Somewhat similar cationics (quaternary ammonium salts) are commercially available in squirt bottles for cleaning hard surfaces. And cationics can be very effective because they often adsorb or adhere to surfaces better than nonionics or anionics. This could be a key to your success.
We don't know what kind you have on your car, but water-based acrylic polyurethane enamel paint is currently the most widely used auto paint (https://en.wikipedia.org/wiki/Automotive_paint).
These common paints would have polar amine and carbonyl groups; the cationic surfactants would better attach to the polar paint surface - not necessarily emulsifying the road tar and bugs - but preventing redeposition of tar and bug parts. So wiping would knock the dirt off, and the cationic surfactant would help keep it off.