A Volkswagen Jetta averages about 43 additional miles once the gas indicator light turns on. Most newer car models are designed to go anywhere from 30 to 50 miles once the fuel light activates.
Though it's possible to drive another 40 miles or so on an almost empty tank, it is better for the car's health to refill once the gas gauge reaches one-quarter full. Driving on or near empty is particularly hard on the car's fuel filter, causing it to become blocked with sediments that can cause overheating. Driving on low fuel also adversely affects the car's brakes and power steering.