Headlights technique taught to me by the veritable King of car photography, Taly Noy.
Smallest possible aperture and if needed an ND filter to slow the exposure right down. Longer the better Have assistant inside car but out of sight. (Weight of assistant as a bonus lowers the vehicle's suspension making it look even sexier). Start exposure with lights off. After an appropriate time has elapsed get assistant to turn on lights for a second or so then off again.
Job done. If there is no assistant you can cap the lens while operating the lights yourself.