Free wheeling, coming to a VAG model near you soon. Quote from Audi Q3 web page:

"Transmission S tronic®

.... When the car is moving but not accelerating or braking, the S tronic® dual-clutch transmission disengages the clutch and allows the Q3 to roll freely (if Audi drive select is ordered and efficiency mode is selected). This enhancement helps to save even more fuel."

When the car is moving but not accelerating or braking or to put it another way: when it is travelling at constant speed

And exactly how many hills will you coast down where you can maintain a constant speed?

Without

1) accelerating due to gravity

OR

2) braking to reverse that acceleration and stay within the speed limit.

OR

3) slowing because the hill isn't steep enough to maintain momentum

There is a very narrow range of shallow gradients where there is not quite enough gradient to allow the vehicle to maintain speed in gear with foot off throttle; where the engine braking would be too strong a feather touch is required on the throttle to maintain speed. In this very narrow band coasting in neutral will reduce fuel consumption. As soon as the gradient gets steep enough to overcome engine braking then better fuel consumption will be achieved by re-engaging the drive. The Audi system will detect these circumstances and determine whether the drive would be better engaged or disengaged. It will not, however, free wheel in neutral down every hill it finds.

Fact (I know you don't like them but...)

In my 1.8TSI DSG:

Rolling down a gentle slope in 7th gear at just over 40mph foot off throttle - maxidot fuel consumption reads 0.0 litres per 100km.

Coasting at same speed down same gentle slope in neutral - maxidot fuel consumption 0.8-0.9litres per hour. At 40mph that is 0.8 litres per 40 miles = 50 miles per litre = 80.5km/litre = 1.24litres per 100km.

So! The difference is small but clear - in gear: 0.0litres per 100km whereas coasting in neutral: 1.24litres per 100km

QED!

If you want to repeat my test the road I used was the A65 in West Yorkshire between the Fox roundabout at Menston and the Burley-in-Wharfedale bye-pass roundabout.

48.4 mpg according to the maxidot on a 70 mile trip yesterday.

Granted most of it was dual carriageway doing 60-70mph, I was driving gently, it was a nice day but aircon was off and I am running a tank of V-Power through, but still not bad out of the 1.2TSi

The maxidot has compared closely to my measured figures so far.

Have you guys turned off the Aircon recently?

No Seriously, in my Roomster I noticed an idle consumption of 1.2 l/h with the aircon on and 0.7 l/h without (Climatronic), so there is definately a difference even though it is probably not this big over longer driven distances.

Edit typos

If you re-read my OP you will see that the improved figure was with the aircon ON.

I normally drive with the aircon OFF.

This was one of the reasons I was so surprised with the figures

The air con seems to make more difference on the petrol engines than the diesel, which seem to like loads and perform at their best under load.

Last two fill to fill mpg figures have been 46.6 and 46.7 respectively, with a 45.8 before that. Be nice if it could be maintained, however I can imagine the winter months will drive it back down :(

Despite the above Fuelly figure is looking a bit low, mind it does include the holiday mpg with 3 adult passengers and softbox on the roof

TP

Last two fill to fill mpg figures have been 46.6 and 46.7 respectively, with a 45.8 before that. Be nice if it could be maintained, however I can imagine the winter months will drive it back down :(

Despite the above Fuelly figure is looking a bit low, mind it does include the holiday mpg with 3 adult passengers and softbox on the roof

TP

well, it is 7mpg better than my DSG average......but I think if I was driving 'normal' use, i.e. not around South London all the time, then it would be around the 40's.

Mke