450 kms is a little low. I did 521 kms to a fill up, and had about 4 liters of gas left in the tank. If I ran it to empty I might have got 475 to 500 kms.
When you say empty, what do you mean? Where is the needle on the gas gage? How many liters did it take to fill it up again? The fuel warning light comes on a 1/8 of a tank, not completely empty.
What year is your car?
Where are you from Joce? Why not take a minute and introduce yourself in the Introductions for New Members area?
2001 Bonneville SSEi (retired at 365,000 Kms.)
2014 Jeep Grand Cherokee Overland (yes, I know its not a GM)