Coasting in neutral fuel consumption?

Belloni

Belloni

Belloni

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17 Feb 2009
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My girlfriend just got her tax letter in the post and I read the leaflet it came with.

Now I know that coasting is dangerous etc but the leaflet claims it uses more fuel?! Getting mixed answers when googling!
 
When you put the car into neutral, it is the same as having the engine running while stationary.

If you are moving downhill without touching the accelerator, then the motion of the car is turning the engine, and uses very little fuel to keep it running.
 
PhillyDee said:
When you put the car into neutral, it is the same as having the engine running while stationary.

If you are moving downhill without touching the accelerator, then the motion of the car is turning the engine, and uses very little fuel to keep it running.
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Yep, leaving it in gear and rolling will use far less fuel, and in some cases, no fuel at all.
 
Depends on the situation. In just about all EFI cars, the injection will shut off when the throttle is fully closed and rpm is above the threshold for cutoff.
 
It is completely dependent on the situation. I would say that a more sure way to save fuel is to brake less by reading the road ahead.
 
PhillyDee said:
When you put the car into neutral, it is the same as having the engine running while stationary.

If you are moving downhill without touching the accelerator, then the motion of the car is turning the engine, and uses very little fuel to keep it running.
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Even just going along on a flat surface probably switches off the fuel injection until a certain point - the difference in engine braking force vs coasting braking force (i.e. rolling/air resistance) is caused by the resistance of the pistons and driveshaft.

Of course if you were in space you would continue moving at a constant velocity when coasting :D
 
Coasting in neutral is stupid due to control reasons. Clarkey is right about the ecu too... Drivers amaze me. In fact, I shouldn't be surprised, they'll spend stupid money replacing a car to attempt saving pennies so coasting in neutral to save mpgzzz is hardly out of this world
 
Why not just use the clutch to coast instead of using neutral? You can always move into gear and accelerate when necessary?

Doubt you'd save much though unless it's downhill all the way.
 
anyon said:
Why not just use the clutch to coast instead of using neutral? You can always move into gear and accelerate when necessary?

Doubt you'd save much though unless it's downhill all the way.
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You would not save any, in fact, you would use more.
 
The only situation where you may save fuel would be on a slight downhill, where you still need some throttle to maintain speed, but can maintain speed fine in neutral.

Other than that, you'd be best off just leaving it in gear and twiddling your thumbs :P
 
If it's an older carburetted engine then it will use less fuel coasting in neutral. If the momentum of the car is forcing the engine round it will be sucking excess fuel through the carburettor. But coasting is a bad habit to get into so don't do it :D
 
I was told that over around 2500rpm, if the throttle is closed, no fuel is used as the motion of the car is keeping the engine turning over. In neutral, fuel is required to keep the engine running.
 
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