Yesterday I had half a tank and filled all the way up and the gauge read 3/4 full.

Today I went on a road trip and ran it empty. my "Fuel Level Low" text came up on the DIC and I filled up, now the gauge is below the E line and the DIC reads "LOW MILEAGE" where it normally displays the miles left till empty.

Im going to pull the battery cable tonight and hope it resets something. What could cause this?

EDIT: Was able to get the damn forum search working and found a tip about clearing codes, that worked. Is this going to be a reoccurring issue? Is there something in the car that is failing?