I've never tried to do something like that but if it's any use: My fuel gauge has 8 bars on it. When i burn off the top two my tank is approximately half empty. I don't know how linear it is below that but it drops quicker than the top two.
When i'm filling up and i let the pump trip out normally and fill no more, the gauge will start dropping more or less straight away. Which tells me that's the way the system is designed. Then you get guys like us filling to the brim and we are in a situation where the needle doesn't move for ages until we burn off the fuel that went above the fuel gauge, so to speak.
ollie
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