With cars especially it depends a lot on textures and how they are placed together with the alpha channels,ahha yes yes, i still have to learn kseditor!
well for me personally it is anyways,
you could copy a material setting from 1 car and place it on another, but depending on how the textures was formed and specially like I say the alpha channel / speculars built into the textures will give totally different results, its a case of studying textures and materials side by side to extract the most potential from the shader.