I had the pleasure, (extreme pleasure) of driving an RS4 Cabrio for 11 days in California. I currently own a measly Mazda 3 (5spd MT) up here in Ontario, and to try and save on fuel, I frequently coast with the car in neutral whenever possible, figuring that the engine running at idle speed is using less fuel than at 3000 rpm or so, while in gear.
So I'm in California with the RS4 and coming down a long hill and follow that same 'neutral' routine (because that beast gulps fuel), and a friend of mine tells me that if I leave it in gear, the fuel shuts off and the engine only runs on momentum until I step on the accelerator again. Therefore I'm using more fuel in idle than while in gear.
I find that hard to believe, but looking for input from some Audi owners.

 

Very true, as far as I know it also states this in the user manual

 

any idea if this is a Audi Specific feature? I'd like to know if my Mazda 3 does the same thing.

 

I know I am quoting myself on this but I was partally wrong I dont think it shuts off the fuel line as the car would power off, I have heard this with the hybrids but not sure if the Audi does it

 

does anyone else have any experience with this?

 

If the vehicle is decelerating below 2500 RPM, it trims the fuel usage.

However, there is still the 'drag' of being in gear (try coasting down a hill in neutral and in 2nd gear and you will see what I mean).

If you are in a high gear (5th or 6th), shifting to neutral will have no affect on the coasting ability of the vehicle but in daily traffic, you can save quite a bit of fuel by 'neutral coasting' to red lights, down hills, etc.

 

My RS4 is the same. When "cold" and in neutral, the fuel consumption will sometimes stay
higher in neutral. Funny, the revs don't go higer, just the fuel consumption on the computer.
Once the car warms up it will drop down to 0 when in neutral.

 

Well in gear it makes sense but when the clutch is engaged in gear then there is no "drag"