I guess the answer as to why you can only put 13 gals in is because that is all you have used, regardless of what the gauge says. Let alone the light.
A couple weeks ago, I let it go until my light came on, and that happened at about 380 miles. When I filled up at 397 miles, I still only put in just over 14 gals.
The lights come on way early, relative to empty.
You just have to learn your car's timing on the light, have an idea of your current mileage and interpret everything accordingly.
Example: During winter mileage times, at 1/4 tank gone, I'm typically at 125 miles, in summer it's 150 miles. At 1/2 tank it's 225/250, at 3/4 tank gone it's 300-325/350 miles. Light comes on somewhere around 1/16 tank remaining (gauge not actual).
The light is just there to tell you to start looking for gas, not to tell you how much is left. There is no calibration on when the light comes on, that I'm aware of. It's a warning only, not a data point.
A couple weeks ago, I let it go until my light came on, and that happened at about 380 miles. When I filled up at 397 miles, I still only put in just over 14 gals.
The lights come on way early, relative to empty.
You just have to learn your car's timing on the light, have an idea of your current mileage and interpret everything accordingly.
Example: During winter mileage times, at 1/4 tank gone, I'm typically at 125 miles, in summer it's 150 miles. At 1/2 tank it's 225/250, at 3/4 tank gone it's 300-325/350 miles. Light comes on somewhere around 1/16 tank remaining (gauge not actual).
The light is just there to tell you to start looking for gas, not to tell you how much is left. There is no calibration on when the light comes on, that I'm aware of. It's a warning only, not a data point.