It depends on the vehicle, but generally speaking, you can drive about 50 miles with the gas light on. This is because most cars have a reserve tank of gas that holds about 2 gallons. However, it's important to note that this is just an estimate and the actual distance you can drive with the gas light on will vary depending on a number of factors, such as the size of the gas tank, the fuel economy of the vehicle, and how much gas is already in the tank.
If you're ever unsure of how much gas is left in your tank, it's always best to play it safe and refill as soon as possible.
