Fill your gas tank when your tank is on "empty." Pump the fuel until the pump automatically shuts off, indicating that the tank is full.
Reset your odometer to zero.
Drive your vehicle until the gas tank is on empty again.
Write down the number on your odometer before you fill up with gas.
Fill your tank again, being sure to stop when the pump automatically turns off.
Write down the number of liters it took to fill your tank.
Divide the kilometers from the odometer by the liters it took to fill up your vehicle. The result shows the kilometers per liter that your vehicle used for that tank of gas.
Perform the previous steps several times for increased accuracy regarding liters-per-gallon usage.
