Brett Bailey

Experiment with your shutter speed. Perhaps, 1/250. http://vimeo.com/45537299#

I have to echo some of the comments made thus far. Car stuff is dangerous. I would reommend one of two options. 1) Poor Man's Process - Have a light gag that swivels across the windshield to simulate passing street lights. 2k bounced into the windshield for ambient. Then have a tweenie in the rear simulating cars from behind. You could also have a unit with red gel to simulate the tail lights of passing cars. You could even throw up a rig with Cucs. Here's another example: http://www.nbc.com/law-and-order-special-victims-unit/production-blog/for-those-of-you-out/ 2) A hood mount for the camera. I've always liked this set-up. One of my favorite car scenes was in "To Live and Die in L.A." You still have to be very careful. It would be similiar to 1:33 and 2:41 below.

All the comments here are really good. We're assuming you're trying to achieve the following look. (See: 0:52)

The breath effect is caused by water vapor being added to the air by your lungs on a cold day. When your breath leaves your body and comes in contact with the cold air it's cooled. When the vapor is cooled, it condenses into tiny water droplets like fog. Under most circumstances, you will see this effect occur around temperatures below 45°F with a relative humidiy at about 50%. You could also add the effect in post, if the environment isn't conducive to what you're trying to achieve. (See: Particular/Video Copilot). It will need to be backlit to see the effect in the ideal environment. And, as others have stated, you will need a fogger and a focusable light to produce a "light shaft." http://www.videocopilot.net/tutorials/frosty_breath/

I'll second Travis's comment. I highly recommend "Adblock Plus","DoNotTrackMe", and "MaskMe."

Personally, I would lean more towards renting a camera. You have to remember "Moore's Law" in regard to technology. They are both fine cameras.