I just finished my project of Peugeot 307, I saw many tutorials of car rendering, but very few with the combination of  mental ray and 3ds max. So I decided to make one :)
I will use the 3ds max 6.0 and mental ray for this tutorial, and also my Peugeot Model.

1)Start 3ds max, first thing we need is to change the default renderer of max, open the Rendering dialogue box.

2)From "Choose Renderer" Dialogue box choose Mental Ray, and click ok.

3)The Rendering dialogue box will change with the addition of more and different options.

4)Now its time to make "Car Paint" material. Open the Material Editor, and click the "Standard" Button.

5)From "Material Map/Browser" Select "Shellac", and click ok.

6)Discard the Old Material.

7)After these steps the material editor will look like this, Click the Base material to open its editing options.

8)Click the diffuse map slot, and select "falloff" from Material/map browser.

9)Change the black and white colors to the colors shown in the picture below.
Top Color is R=200,G=0,B=0 and bottom Color is R=16,G=0,B=0.

10)Now modify the Curve in Mix curve option, as shown in the figure.

11)Click go to parent button and set the Specular level and Glossiness values as shown in the figure.

12)Click go to parent button once more and then click the shellac material slot.

13)Click on the standard material option, and choose Raytrace as new material.


14)Again click the reflect map slot and select Falloff from material/ map browser. This time we will use "Fresnel" options instead of default "Towards/Away", also change the Index of refraction option to 2.5.

15)Click go to parent change the diffuse color to black, and also change other values as shown.

16)Click go to parent once more and change the Shellac color blend value to 85.

Next : Scene settings