Originally Posted by Joes74challenger
on newer cars i always thought that was the point of why the gauges all peg then return to 0 and back up to the actual reading at each ignition key initial cycle? i thought they self calibrated already?
What you describe is the gauge reflecting the position of the level sensor. The calibration I was talking about was how well the level sensor position reflects the actual volume left in the tank. Calibrating the level sensor would entail filling the tank to 3 or more known volumes of fuel and taking readings from each.
For sure, this cannot be done on each car in production.
Instead, I suspect something like this is done to several cars during product testing - maybe 100, maybe more - to characterize the gas gauge system. From that they will derive the typical values, and use those numbers to set up the relationship between level sensor (voltage) and the gauge.
But I'm sure the variances on this system are way wider than, for example, cylinder bore dimensions
That is, the real world tolerances on the fuel level will be on the order of ±1 gallon, but if it could be calibrated with cylinder bore accuracies, it would be on the order of ±1 teaspoon