Can a gas tank accept more gas than it's capacity?

I think it's because you overfilled it. The volume of the tank does not include the pipe/hose that connects the gas port to the tank.

While I suppose the tank may hold more gas than stated, the filler tube (the hose from where you put the gas nozzle to the tank) is probably the culprit. I've heard it can hold up to an extra gallon of gas in some cars.

Here in Canada all gas station pumps dispense and charge based on a corrected volume. As gasoline density varies with temperature the amount you would recieve by weight varies for a given volume. I always get more gas in the winter in my tank then in the summer. Your local gas station my be doing the same.

Gas Tanks or any tanks have a percentage for ullage. This ullage is there to provide safety and expansion in the tank.

It is possible for your Toyota Camry to filled up extra 4 gallon of patrol from 18.5 gallon capacity fuel tank to 18.89. Some car manufacture always round up the numbers (in this case, your fuel tank capacity) to the nearst number. For example; if your car fuel tank capacity is 18.80 gallon, they will usually round it up to 18.5 gallon and not to 19.00 gallon. This is to prevent the fuel tank over filled. The other possiblity is that someone at that patrol station had done some dirty trick on the patrol filling hose by draining out the balance patrol inside the filling hose. Usually, for car owner, they will not notice this trick but for motorcycle it is easly detected because motorcycle had the "Constant" patrol filling and cost. The 3rd possibility is that "Does your fuel tank capacity included the Emergency patrol level". My friend Toyota Camry can go extra 60KM after the "RED" light start flashing.

Everyone, thanks for your help. I guess I have more capacity than I belived. No need to go back to the gas station with anger filling my head.

There is some volume of fuel in the car tank that is not usable. So you would think that the usable volume would be less than the published volume. One would have thought that if you were that low, the car would have stalled and sputtered coming to the fuel station as you were going up and down grade. I don't think that the temperature of fuel varies all that much between summer and winter. It is stored in ground tanks that are not that much susceptible to ambient temperature fluctuations. I have seen people shut the pump off and then hold the pump handle on while raising the hose up high to drain as much fuel trapped in the hose as possible. An unscrupulous person might be able to a dollar more fuel that way, but then the next guy gets short changed. By the way, on pumps with multiple grades and just one hose, people who buy premium grade fuel are probably getting short changed every time they buy gas. If the price of gas keeps escalating they should redesign the pump. It would be easy to put an automatic valve in the handle to close if the pump switch is off. Solving the problem of dispensing multiple grades of fuel through the same hose would be a bigger problem to solve without having to run two lines to the handle.