[momo3605]

When slowing down, once i get to about 40mph, even while braking, the mpg counter drops to like 60mpg, this is pretty dumb...i thought with the efficient dynamics, battery charging/auto start-stop eco facade, it would atleast be able to be gasless while slowing down. Even my M3 stays at 99.9 mpg up to the last second before coming to a complete stop.

[SomeRandomer123]

I get 99.9 on the live MPG read out (BC) on the Black Panel when decelerating and the red live MPG on the full Black Panel display goes into the EfficientDynamics blue area as Brake Energy Regeneration is taking place.

When coasting or braking (decelerating), the alternator engages to return charge to the battery. Our alternators are not engaged at all times so load on the engine is reduced - thus giving full engine power and maximum efficiency as the engine does not have to work as hard.

As I believe, but can't confirm 100%, the engine uses no fuel when decelerating (off the throttle) as the spinning wheels are obviously turning the transmission, which is turning the crank, which is driving the pistons.

I do want to learn more about what the engine and engine management is up to with regards to fuel efficiency when decelerating - especially as the new ECO PRO mode is supposed to disconnect the transmission (N) when decelerating to save fuel. Bearing in mind what I've just said and believe to be true, surely the idling engine is using more fuel than the decelerating engine?

[momo3605]

Really? I'm not getting 99.9 when slowing down. But I have found that once my rpm's fall below 1200 or so, the transmission disconnects from the engine and then the mpg drops to 60ish cuz I guess the engine has to turn back on. If I put the car into S and slow down, the transmission stays engaged and I stay at 99.9 up until right before I stop.