My low fuel indicator comes on when I have plenty of fuel
The fuel tank on all '89-'95 Taurus SHO's has a capacity of 18.2 gallons. Some owners of newer cars ('94 and '95 models) have noticed that the low fuel indicator comes on with as many as 4 to 7 gallons remaining. That's 80 miles of range in city/suburban driving, and may seem excessive.
There is a reason for the large margin. Keep in mind that the fuel pump is submerged in the fuel tank. The fuel running through the pump is used to lubricate and cool the pump before it is used to smoke your tires.
Ford had fuel pump failures that they believed were caused by overheating. In order to reduce the occurrence of failure, they changed the guages to read less gas than is actually available. This is intended to ensure that the pump remains submerged provided the driver fills up soon after the low fuel indicator comes on.