Originally Posted by TheLex
It may be the temperature difference as the tank and the liquids inside expands and contracts depending on the weather. Seems like it happened to the both of you when the temperature of your car dropped and the fuel gauge just read the levels wrong because of the contraction. This is just a shot in the dark of course so don't take it as fact. Maybe someone may have a better answer.
That's something i've learned with my other cars especially since I park outdoors and where I park the vehicle is on a decline, so you can imagine what that'll do for the fuel level reading.
Best thing to do is to let the vehicle warm up completely and drive on level road for 10-15 minutes, that should bring the fuel level where it needs to be.