How does a fuel gauge work when driving when the fuel is shaking?
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Older fuel gauges have a buffer module that acts to “smooth” the signal to avoid fluctuations due to fuel slosh. Many classic cars have no buffer whatsoever, and operate on simple resistance at the sending unit. On those, you’ll see the needle move on the gauge quite frequently.
Newer gauges which communicate with an ECU have a running table of values, so the fuel sender signal data is recorded at some interval. The table of values is averaged, so an outlier value gets “lost in averages.” If you have high and low values from sloshing, they’ll average to the true level with enough data points. As the newest data point enters the table, the oldest data point is purged.
Plus, some modern fuel tanks are designed with baffles, specific shapes, or split in the vehicle’s frame/body to help eliminate unnecessary sloshing and aeration. Aeration in fuel (bubbles) is not a good thing in any metered system because air is compressible, compressed air builds heat, and the change in volume and throws off metering (like opening a bag of potato chips and seeing that it’s mostly air).
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