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I am puzzeled by the fact that when driving downhill with a gear engaged, the accelearator not pressed, the display in my 2014 Giuliettea indicates that the engine uses fuel. My old Passat always indicated 0 fuel consumption in this situation. Is this unique for the 1.4 Multi Air engine?
 

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It should show 2 litres / 100 km. And it's normal for Fiat Group. My Peugeot shows 0. And the consumption meter is pretty accurate, at least in MultiAir. In my case it's always + ~0,2 l / 100 km.
 
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I am puzzeled by the fact that when driving downhill with a gear engaged, the accelearator not pressed, the display in my 2014 Giuliettea indicates that the engine uses fuel. My old Passat always indicated 0 fuel consumption in this situation. Is this unique for the 1.4 Multi Air engine?
If the engine is ticking over it would still use fuel as combustion is taking place. Apparently, 0.1-0.2 gallons per hour, at ~0.1 idling at 600-800rpm (warmed up) and ~0.2 at 800-1100rpm (cold idle, A/C, extra load, etc.)
 

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My understanding is that with modern fuel injection systems no fuel is injected if the motion of the car will keep the engine turning over such as when going down hill, in gear and with foot off the throttle.
 
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My understanding is that with modern fuel injection systems no fuel is injected if the motion of the car will keep the engine turning over such as when going down hill, in gear and with foot off the throttle.
That's interesting, I hadn't heard of that before. Found this on another forum:

You use no fuel while coasting downhill in gear. Reason being, the injectors are at 0% duty cycle (off). If you are in nuetral, the injectors have to keep the motor idling, so fuel useage is minimal but not zero.

When you coast in gear, you are using the momentum of the car to keep the motor spinning. Since the motor keeps spinning, and you arent giving it any throttle input, the injectors turn off. The ECU calculates that zero fuel is required to keep the motor from stalling. Sometimes you increase speed going downhill with no throttle because the rotating mass isnt more than the inertia of the car, so you speed up a bit.
 

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My 2011 G shows 2L/100km, which I figured was a false calibration value, sorry I mean an Alfa Romeo feature. :idea:
I have met a few calibration people in my travels and yes on the downhill/over run, the engine is in fuel cut mode.. So it uses effectively 0L/100km.

Previous GM, Mazda, Toyota, Ford have always shown 0L/100km.
 

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My DS3 shows 999mpg on the over-run. Just as an experiment I tried coasting in neutral (don't do this at home,folks!) down a long hill with the engine running - it indicated something like 200mpg.
 

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My G 120TB shows 0L/100 km when on the overrun - my previous Bravo II 120TJet (same engine) did the same.
Sorry guys, I have remembered this wrongly. My speedo is set at km and litres. Going down hill accelerator closed it shows 1L/50km = 141miles/1 gallon. I tested it yesterday on a slow ride in lovely sun shine.
I usually have the economy meter on average km per litre since last refill. Usually 15,5 km / L = 44m/gallon.
It does lots of short journeys.
 
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