Iv just filled the tank up from almost empty and something strange happened..

 

after driving about 5 miles the needle has dropped to 3/4 full and the range has gone down. I can’t see any leaks and the cap hasn’t fallen off 😆. 
 

Any idea what might have happened? 

Check whether or not your outside temperature readout is giving a sensible number, that and the fuel gauge sender share a voltage feed.

6 minutes ago, Breezy_Pete said:

Check whether or not your outside temperature readout is giving a sensible number, that and the fuel gauge sender share a voltage feed.

Temperature seems about right 

Someone must have had a similar problem? 
 

Anyone 

Replace the fuel tank sender if it bothers you.

Another possibility is a cracked solder joint on the connector from the instrument cluster circuit board. 

Try giving the whole area a bit of a shake by hitting with your palm on top of the dashboard, see if the reading on the fuel gauge changes.