You know every car is differant. Our Honda CVR can go near 30 miles when the light starts dinging. Other cars and the type of driving you are doing are going to vary. My son was in a jeep cheokee and said the low gas light came on , but he figured he had 20 or thirty miles, till he was tryuly empty. So he ran was errands on the way home. Later that night he had to pick up his girlfriend from work and thats when I got the call to HELP bring gas.
So if you have a system that tells you your getting low, take notes of how far and dont push it to much or you may get stuck out in the woods somewhere.
My gas light comes on when I have about 2 gallons left. Basically enough time to get to a gas station.
Since I don't even own a car, I never have to worry about this.
i think it leaves you with enough to get to a gas station soon!