I've made it at least 30-40 miles when my light comes on. I estimate that I've got around 4 gallons left when mine hits since I put in ~14 if I fill it right as the light dings. Guessing it's probably more based on the tank design, but you might try running some bottles of Techron or similar through the tank. Supposed to help clean up the level sensor, so you might get more consistent readings. I did a long drive this weekend and got 211 miles on the first half of the tank, but only 90 on the second half. Went through another tank and it was a little closer, more like 180 on the first half and 150 on the last. Have a suspicion that my gauge isn't the most consistent reading from time to time. For instance, I can park the car at work in morning with a 1/4 tank, but when I go out for lunch it will be just under a 1/4 when I start it up and just over a 1/4 after things warm up.