The fuel gauge only goes to about 6 gallons, no matter what the amount of gas is (above 6 gallons). once it gets below 6, it's somewhat accurate.

On occasion, especially after driving on a bumpy road, it will read accurately, until I re-fill it again once it gets below 6.

But most of the time it reads 6 gallons, and occasionally it'll stop below 6 if I fill up the tank below 6 gallons.

i.e., if it drops down below 6 and I fill, it stays there until a random time it'll reset to 6 gallons.