At the end of the day the fuel gauge is notoriously rubbish for getting an accurate read, if the pump has been changed there's a chance the sender unit/float could have been damaged and giving further wonky reads,
1/4 used on the top half of the tank is more like 1/2.
When my gauge hits half full it takes nearly 30l to fill it back up, again with the final 1/4 full the low fuel light may decide to come on randomly or I can do 120miles and the light won't even flicker but the needle will be below empty
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