I have to admit, I got this information from here via a 3rd party. But I verified the results with my scanner.

The engine keeps turning because the car is in motion- the transmission, even an automatic, keeps the engine turning over until a certain point. Then it has to idle on its own so that it doesn't die- injectors open back up and the idle air motor forces air through.

If you have access to a OBD scanner, you can see this. Foot off gas in gear drops fuel consumption to zero and fuel economy pegs out. This does not happen if you coast in neutral. FE may still max out, but fuel consumption will be nonzero.

I am not entirely knowledgeable in the details- it was a surprise to me when I learned it too. And it may not be true for all vehicles.

http://www.greenhybrid.com/discuss/n...navy+injectors