I had to replace my fuel level sender a couple of months ago after it failed. The old one one would stay on full for about 50 miles then move down. I'd get the low fuel light with about 3 gallons left. With the new one in, it starts down from full within 10 miles but the low fuel light comes on with 5-6 gallons left in the tank. I'd say they're all different from my experience and reading the other replies.
I'm N/A and my mileage is around 29 when I'm on a road trip and around 20-22 around town. Much worse lately though. The AC is bringing that down fast with the 90-100 degree temps we've had!
