Fuel level gauge calibration.
 

The past few days my fuel level gauge seems to be out of whack. It goes empty when the gauge says there should be 1/3 of a tank left, it also says its full when I've burned through about 2.5 gallons. Is there a way to recalibrate it?

Not that I know of. I fill up, and after 80 miles it starts to drop. and begins to plummet once I hit 180 miles.

OK, it still gives relative fuel level, so I don't think the fuel level sending unit is gone, it just annoying to run out of gas when your meter says you still have 1/3 of a tank.

then it's time to go with mileage and refill it when it reaches a threshhold. I normally refill mine around 300 miles. that seems to be a good mileage for me. But I normally drive a mixture of highway and local. If you drive mostly highway, it'll obviously go longer per tank. I believe the sending unit is a non-repairable item hence it would need to be replaced as a whole; I might be wrong here.