If your car is "modern," (i.e., made in the past 20 years), then I may not be understanding your concern. But on my old jalopies, I've been happy with Griot's Vinyl/Rubber Dressing, Z16 (named "Tire Dressing," but actually good on all rubber and vinyl), and (most recently) Mother's Preserve. For plastics, I've been happy with AIO/SG.