I live in a mountainous area with 6%-7% grades, so I often drop down to a lower gear when descending long hills, so as not to ride my brakes. I'm surprised at how little this 380HP engine holds my car back even in 3rd gear. I wonder if the ECU keeps some small amount of throttle on, even during descent?

 

You could check the instant fuel consumption to see if there is any fuel going in, should get you to the answer you need

 

I'll do that in a couple of days and report back. My Acura Instant MPG pegs when I do that, so checking Instant on the A-M will be interesting.