Fuel consumption, coasting vs. in gear

[saskak]

Hello berlingo members,

If I was going downhill what would be better in terms of consumption, coasting in neutral or being in highest possible gear?
I am aware that one might loose some control if the car were to be in neutral, but purely from consumption point of view.

The onboard computer states that in gear the car consumes 0.0 litres of diesel, i.e. nothing or close to nothing. In neutral, surprisingly it shows 0.5 litres/km (~565mpg). In neutral the rpms drop to ~800-900, but in gear depending on the speed of course ~2000. If the rpms are ~2000 or higher as compared to being in neutral, would the consumption be always greater, unless there is no fuel supplied.

Any opinion is more than welcome.

[Lighty]

I think it will depend on the year &type of car, a hdi will be clever enough to shut off all fuel.
However if you coast, there will be no engine drag, so the car will travel further with its momentum, so this is definitely most efficient.
Modern vehicle design calls it "sailing".

[saskak]

I think it will depend on the year &type of car, a hdi will be clever enough to shut off all fuel.
However if you coast, there will be no engine drag, so the car will travel further with its momentum, so this is definitely most efficient.
Modern vehicle design calls it "sailing".

Many thanks for the answer. I was thinking of a relatively modern hdi, but did not really consider the engine drag. In this case, if one needs to maintain a certain speed, say 50mph, then the fuel shut-off and as long as the car can keep the speed, e.g. enough slope, the in-gear should be better in terms of consumption.

[ron]

You've got it.:woop:

[coxyboy123]

If your vehicle is fuel injected, it will use less fuel in gear as the engine management will more or less completely back off the fuel injection in Relation to the throttle. When in neutral, an amount of controlled fuel is injected to sustain a steady idle. So, in theory, it is more efficient to coast in gear. Just depends how far you can go when you factor in engine breaking.

[klberlingo]

every time i go to a particular town near me theres an incline for nearly 5 miles and if you hit the crest at 50mph you can 'freewheel' in neutral or 5th and maintain that speed all the way to the 30mph limit sign.. does wonders for the mpg figure

[ATL_driver]

in gear, more control of the vehicle too, coasting in neutral is bad!

[j90xxx]

in gear, more control of the vehicle too, coasting in neutral is bad!

Isn't it illegal? illyme:

[ron]

in gear, more control of the vehicle too, coasting in neutral is bad!

Isn't it illegal? illyme:

Yes,it's illegal.

[j90xxx]

Thought it was.
So.
Don't coast. It's against the Law.
And coasting uses more fuel.
Doesn't anyone listen to Clarkson. illyme: