“I have not tried turning off the key but I frequently shift into neutral when rolling down long grades (not supposed to do it because you have less control over the car but it saves gas).”
Remind us all where you drive so we avoid your environs. It’s amazing to me what some will do to save pennies at the expense of their own personal safety. Also, if your vehicle has an automatic transmission, it won’t be happy with your “coasting.”
Then, there are all the rest of the automatic transmission cars and trucks, that will be mechanically damaged by coasting in neutral. The transmission will be ruined in fairly short order from attempting to coast with it in neutral.