Ok, my first thought... That's a REALLY hard shadow, kinda like you got from early versions on Poser. But I live in the UK so sunlight like this... enough said. So I looked around google images and I'm kinda right. If the sun is overhead then a shadow under the car is very dark, anywhere else I think the ambient light would mute the effect somewhat. I do understand it's the render engine, not you. Shadow aside this is another great render.