If you discover that you filled the vehicle's fuel tank with the wrong type of fuel, do not attempt to start the engine! If you have driven your car after misfuelling, stop immediately! With newer types of vehicles already the central unlocking of the doors (unlocking in newer vehicles begins the process of preparation for ignition, heating of spark plugs, pumping of fuel into the system for direct injection, etc.) can prove as lethal, therefore do not press the button »unlock« on your key!
As soon as you realize your error, call your local tow company, which will pump out the contaminated fuel and dispose of it in an appropriate fashion. At your local car service dealer also check all seals and filters, which are in some cases destroyed even if the car had not even been started after misfuelling.
It physically prevents entry of the wrong type of fuel
It enables fast and simple fuelling without the unscrewing of the cap (as for example in Formula 1)