Evening Fordmodders.

Does anyone have any idea why my fuel gauge likes to have a mind of its own?

An example would be If I just filled it up it would not move down a millimeter until about 100km's then suddenly drop to 3/4 tank, but then go down even further to 2/3.. then go back up to almost full again. And then it would change if I was to turn the car off and back on again.

Also my trip meter seems to change its average L/100 whenever I turn the car off. I'll get 12ish L/100 when driving after being reset, but then if I turn the car off and back on after a few hours it suddenly jumps up to 15.5+

I cannot think of an explanation..