fuel gaege

Ok this is weird...
1993 silverado sportside 350 V8
This morning coming home from work the needle was one needle thickness over the half mark with roughly 220km on the odometer.
Got in the truck a couple of hours ago and it is reading 3/4 tank of gas and almost at 300 km and still over half a tank of gas left according to the gauges.
Now when I first got the truck I would easily get between 300 and 350 by half tank but it's slowly been decrreasing in the past couple of months and today it seems to be back to where it should be
Any ideas what would cause this?
Yes the needle does move in case anyome asks if it sticks as it went from 3/4 tank to somewhere between half and 3/4 by the time I parked it again and turning corners hard the needle does fluctuate on the dash so it is working.
I'm thinking a build up in the line somewheres and finally let go?
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I think using the gas gauge to meter fuel economy is a completely useless practice. The gas gauges on these trucks are great for ballpark figures "yes I need gas" or "no I don't need gas" but far too innaccurrate to be used to measure fuel economy.
Try using your trip meter and litres per fill to determine fuel economy. I'm sure you see that the gauge moving around like yours has does not correlate to fuel economy.
Doc

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I'll have to start doing that then, basing it on mileage and not what the gauge says.

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