Abstract: The maximum full level is determined in a fuel tank of undetermined size using a fuel level sender referenced to the tank bottom. A minimum full value is selected for a given type of tank and when the sender signal goes below a percentage of that value and subsequently goes above the minimum full value, a fueling event is recognized and the current fuel sender value is adopted as the maximum full value. Where a heavily filtered signal is used to minimize the effects of fuel slosh, the maximum full value is subject to increasing to higher values occurring during a short period after fueling to allow recovery of the filtered signal. An empty value is calibrated before the vehicle is initially fueled. A maximum empty level is initially set and if a lower level is measured when the ignition is turned on, the lower level is set as the empty value. This calibration is terminated when the tank is fueled above the minimum full value.