In message , grape writes
More. It uses fuel to keep the engine running, if you coast with the throttle closed the injectors are turned off on a modern EFI car. You can confirm this if you have access to a scan tool capable of displaying live data, check the injector pulse width, it should go to 0.0mS
Apart from that, it's a fairly daft thing to do anyway as you have less control of the vehicle and you stand a good chance of cooking the brakes to the point that they just won't work when you really need them.