I've just started to use blender to make car models using blueprints, I've run into this problem where i have dark and light areas on the panels for example the top half of the front wing is supposed to be all light and the bottom half is supposed to be all dark. I've already flipped the normals, can someone help me?
This is caused due to some faces being bigger than others, and as such Blender reflects the light differently. This happens when smooth shading is enabled, and the angle/size of two or more faces right next to each other differ greatly.
If using a subdivision surface modifier is not suitable to you (This should work with Blender Game engine as well), modifying the faces may be your best bet.
Hope this helps.