Apparatus configured to estimate quantity of fuel stored in vehicle

An apparatus, configured to estimate quantity of fuel stored in a vehicle, comprising:

• a fuel tank, configured to store fuel used for an engine mounted in the vehicle;
• a fuel quantity measure, configured to measure quantity of fuel stored in the fuel tank;
• a filtering processor, configured to subject the quantity of fuel to filter processing by a filter gain to detect an estimated quantity of fuel stored in the fuel tank;
• a filter gain setter, configured to set the filter gain;
• and
• a vehicle status detector, configured to detect which one of a starting state, a halted state, a state achieved immediately after stoppage of the vehicle, and a traveling state corresponds to a state of the vehicle, wherein
• the filter gain setter sets a first gain as the filter gain when the vehicle status detector detects that the vehicle is the starting state;
• sets a second gain as the filter gain, which is larger than the first gain, when the vehicle status determination means determines that the vehicle is in the traveling state or the state achieved immediately after stoppage of the vehicle;
• and sets a third gain as a filter gain, which is larger than the first gain and smaller than the second gain, when the vehicle status determination means determines that the vehicle is in the halted state.