All those measurements were taken with the gas tank empty. Certainly gas will change the equation. But gas is (by its nature) a variable. On serious cars, we set them up with 1/2 tank of gas as a happy medium.
We don't do base weights of the car with gas as tank size and the amount of gas can change your baseline significantly. So, like many people, we "weigh" the car with all fluids and the gas tank empty.
David
