http://www.renderosity.com/mod/gallery/index.php?image_id=1694547

http://www.renderosity.com/mod/gallery/index.php?image_id=1709067

http://www.renderosity.com/mod/gallery/index.php?image_id=1715287

This are three pics from my gallery (there are much more cars and bikes) using different shaders based on bagginsbill and stewer (thanx, and humble myself). An absolute must is an environment sphere (or in a white background a white egg above the car) to give you the reflections.

But with many  cars you run into the "fly shit" problem where FireFly forgets to render polygons and single one polygon black spots appear. The usual remedies suggested here don't help in this case. They don‘t appear when you render the car in Cinema or 3ds max.

The other thing is that lighting conditions are crucial - one main sun light and an IBL is what I usually use.  The first step then is to make an empty scene, light it, and use bagginsbills IBL out  generator to create the pict for the IBL.

The colors in baggins shader or much more difficult to adjust than in the stewer shader - anyway its a lot of rendering trying to figure the color and shades.

But if you are interested in some shaders - or colors - send me an IM