On the car they drop off from Full much too quickly and in fact read 1/4 tank with approximately 12 gallons in the tank. On the bench, they REACT smoothly to downward changes in the arm
That is the shape of the tank. Let's say the upper half of the tank can hold 6 gallons (due to its shape)
The fuel level falls faster for the first 6 gallons then for the last 12.
But if the sender is not calibrated to the tank it will read incorrectly
The sender wire also has resistance that adds to the system so full might show less than full, 10 on the bench plus 2 to 3 for the wire and connections now you are getting 12 or so ohms and the guage will read less than full. Same on the low end will read 80 or so before it really is empty.
