I trickle-fill our MH's gas tank for 8-10 minutes after gas pumps automatically shut off. This always gets me 5-6 more gallons into the tank.
Our family daily driver sedan and our 4X4 pickup truck fuel storage systems act the same way -> I get more gas into the tanks after automatic pump shutoff if I trickle-fill them for a few more minutes.
I suspect that the above situation is the case for the fuel storage systems in most modern vehicles. Why have a fuel tank of "X capacity" ... and then never be using that full capacity?
We like to stop when we want to take pictures, go potty, eat, or top off the tank for plenty of generator fuel headroom when getting ready to drycamp - not just because the vehicle wants to drink.
P.S. I guess that the title of this discussion topic meant "Do you carry heat?" and "Do you carry enough fuel?". ;)