The way you choose to light a car is as important as the location you use and the composition itself. Some times the best lighting is simple natural light, such as sunrise or sunset or maybe just direct sun light itself. Other times a complex lighting setup involving lots of lighting equipment might be the better option. The lighting that best suits the car or situation will often be determined by the colour of the car or the style of the image you are wanting to create.

There is no single 'best' way to light a car. The two images below show a virtually identical image but with different lighting techniques used to take advantage of this cars very dark yet metallic colour. The metallic is accentuated with direct, hard light whilst the dark colour photographs equally well with a clear sunset. One image is not better than the the other, they are just different. The way you choose to light a car will have a dramatic effect on the end result.
 

 

A cloudless sunset or sunrise acts like a huge soft box, the size of the sky itself. This soft light is great for showing the shapes and forms of panels. If you are lucky enough to be able to rely on such sunsets then you should take advantage of them. The lighting setups in studios often try to mimic a cloudless sunset! A dark colour or straight (non metallic) paint might work best with a soft or reflected light, such as sunset, which can create a gentle tonal gradation from light to dark which can highlight curves and shapes much better than a direct light can.
 

Hard or direct light might suit a metallic paint finish because it can bring out the colour, or make it 'pop', much better than a soft light such as an overcast sky. This is where strobes or flashes can be very useful. Strobes can also be very useful for isolating the car from the background by underexposing the background but lighting the car with the strobes, or simply when shooting at night.
 

Strobes where used specifically to make the silver paint 'pop' and stand out from the background. Silver and similar metallic colours respond well to direct light.		The metallic colour in this paint would not have been seen if strobes had not been used due to a drab overcast sky.
Here strobes where used specifically to make the car stand out from the background.		A drab day was exploited and made to look even darker by underexposing the background and lighting the car to make it stand out.

Painting with light is another technique which can be used for its own unique look or simply to light the car without any signs of it's use, either is possible and will be detailed later. Black cars, or very dark colours, respond badly to strobes but can respond very well to light painting with a continuous light source.

This car was shot at sunset, with a strobe lighting the front (radiator) and was also painted with light, using a continuous light source, to help the tyres and wheels stand out better.		Strobes where used to light this car at night however a continuous light was used to light the trees in the distances by walking down the path behind the car and painting the trees with light, instead of the car.
Black cars respond well to painting with light when a continuous light source is used.		This car was painted with light using a strongly gelled light source. This was done so that the ambient (background) light would turn blue when the gelled continuous light source was white balanced in post.

Selecting the most appropriate lighting technique can depend on many factors, some of which are determined or driven by factors out of your control such as the colour of the car or the ambient lighting itself, but ultimately your choice of lighting should be an aesthetic or artistic choice wherever possible.