Seen a lot of complaints on this , Examples complained of gauge dropping quickly when it gets to a lower level . Seems to be a trait with this and other models , years .Whether a new tank unit / sender would fix , I cant say . May , may not .
No it’s not that type of fault it’s the mpg showing when driving it starts off with just blank dashes & then shoots up to silly amounts like 200 mpg & then right down to 10 or 20 mpg & so on up & down all the time ? I might try rebooting it buy disconnecting battery .
Get you now . You can adjust the fuel economy settings + or - with Vag -Com (VCDS ) but yours seems more than that . I have seen some cured by filling the tank on other makes other than Seat , it seems to reset on doing this . Whether rebooting will fix , I cannot say .