Light No Light?

Well,

most times when my gas light comes on I can go anywhere from 30 to 60 miles depending on the way I'm driving. I've figured this out by running it empty which I do not recommend. But on two different occasions I ran it empty and the light never came on. The first time was in St. Louis. I thought something was wrong with the car but found out it was out of gas. Fortunately I was caring my bicycle, because I had to ride it 12 miles to the nearest gas station. The next time I ran out with out my light coming on was today. This time I was stuck on a bridge in the San Francisco bay area. I found out that my road hazard service doesn't cover gas. I didn't have my bike with me and the only tow company that would help would bring me 2 gallons of gas for 80 bucks cash or 100 bucks from a credit card. Thank God my nephew showed up to save me.