coasting in neutral? can this hurt the engine?

I was just wondering if when putting my 2015 Leaf in neutral when coasting down hill will I "hurt" the engine when putting it back into drive? For example, I may be going 50mph and then see a quarter-mile downward slope. I will put the car into 'N' and coast. I may speed up to 54mph. When the hill levels off, my speed will go back down to 50. At this point, I will switch the car back into "D".
I try to do this as many times as I can throughout a 60 mile trip.

I am just wondering if this has any kind of negative impact on the engine or the transmission.

Thanks,
-John

Won't hurt anything, people do it all the time.

But, it's a motor, an electric motor, there is no engine, or transmission.

Yup. Doesn't hurt anything... except your mileage. There is very little benefit to going into N on an EV. If you are coasting to slow down, it can be helpful to avoid regen. However, in the case you mentioned (going downhill, accelerating), you are actually going to end up using more energy with this practice since you allowed the car to speed up to 54 mph. Be better off leaving it in D and letting the regen maintain your 50 mph - then you are recovering the excess energy during your decent instead of burning it off in wind drag.

Driving in "N" reduces your control of the vehicle. It is quicker, easier, safer to just just modulate the accelerator pedal until zero power or regen is used. The power display in the navi, if you have navi, has a finer resolution display. I do this all the time - it's easy with a little practice.

DNAinaGoodWay said:

Won't hurt anything, people do it all the time.

But, it's a motor, an electric motor, there is no engine, or transmission.

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There is a single ratio gear box between the motor and the wheels.
It technically is a transmission by definition, although some people object to calling it that because it is a single gear ratio and no changing gears.

The motor and transmission are still spinning while coasting.
Only the electric power to the motor is at zero power.

If you have just the right grade coasting in Neutral does save a little power.

There are differing opinions on the safe operation of the vehicle in Neutral.
It is illegal in some states, although there are mixed legal opinions on whether those laws are applicable.

I think it should only be done where it does not impact safety.
I usually only do it in very light traffic on long downgrades.

Don't get used to the quick into Neutral by shifting to Reverse.
You will forget and do it sometime at low speed and LEAF will try to come to abrupt halt.
I came close to being rear ended with that mistake one day.

TimLee said:

Don't get used to the quick into Neutral by shifting to Reverse.
You will forget and do it sometime at low speed and LEAF will try to come to abrupt halt.
I came close to being rear ended with that mistake one day.

Click to expand...

+1...Only I did it twice before I decided to give it up.

TickTock said:

Yup. Doesn't hurt anything... except your mileage. There is very little benefit to going into N on an EV. If you are coasting to slow down, it can be helpful to avoid regen. However, in the case you mentioned (going downhill, accelerating), you are actually going to end up using more energy with this practice since you allowed the car to speed up to 54 mph. Be better off leaving it in D and letting the regen maintain your 50 mph - then you are recovering the excess energy during your decent instead of burning it off in wind drag.

Click to expand...

This is false. It will actually HELP your range IF you coast to a complete stop without regen/braking. This means 100% of the momentum is being directly applied to the forward motion of your car, and not restored into the battery. The key is regen is not 100% efficient. Some amount of energy during regen is lost to heat, and hence avoiding regen is preferable for longer range.

However, you must not brake at all for this to be effective.

w4y said:

This is false. It will actually HELP your range IF you coast to a complete stop without regen/braking. This means 100% of the momentum is being directly applied to the forward motion of your car, and not restored into the battery. The key is regen is not 100% efficient. Some amount of energy during regen is lost to heat, and hence avoiding regen is preferable for longer range.

However, you must not brake at all for this to be effective.

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You mean until the actual stop, I take it. I usually apply the brakes (gently) in the last 15-20 feet or so. Now if regen could bring the car to a stop (as it should!!), then I would barely use my brakes at all. 'Coulda shoulda woulda', LOL.

I sure hope they offer a user-selectable regen setting and creep on/off option in the coming model years. How did this idea escape them? (And correct me if I'm wrong, but I don't think even Tesla allows you to set the regen strength, at least not in fine increments.)

I find that with my 2015 SL in B mode, I rarely need to brake. What a concept, driving a car and rarely using your brakes. I am an old guy, and just love being around now that EVs are available. I grew up driving old 1960s vintage VW bugs, what a delightful change.

Not in infinite increments, no, but you do have the option of different levels on a Tesla. You will never be able to have regen to a full stop since regen is also a function of motor speed and thus drops to zero near zero rpm...

mbender said:

(And correct me if I'm wrong, but I don't think even Tesla allows you to set the regen strength, at least not in fine increments.)

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w4y said:

TickTock said:

Yup. Doesn't hurt anything... except your mileage. There is very little benefit to going into N on an EV. If you are coasting to slow down, it can be helpful to avoid regen. However, in the case you mentioned (going downhill, accelerating), you are actually going to end up using more energy with this practice since you allowed the car to speed up to 54 mph. Be better off leaving it in D and letting the regen maintain your 50 mph - then you are recovering the excess energy during your decent instead of burning it off in wind drag.

Click to expand...

This is false. It will actually HELP your range IF you coast to a complete stop without regen/braking. This means 100% of the momentum is being directly applied to the forward motion of your car, and not restored into the battery. The key is regen is not 100% efficient. Some amount of energy during regen is lost to heat, and hence avoiding regen is preferable for longer range.

However, you must not brake at all for this to be effective.

Click to expand...

False when coming to a stop yes but if you aren't stopping and are going down a long grade at highway speeds followed by a level road then maybe true. If going down the long grade would get you up to a speed higher than your usual level cruising speed then the energy wasted to drag will grow.

The key point is to find when that extra drag energy lost at that higher speed is greater than the efficiency loss of using regen.

Yes this energy is gravitational potential energy so by keeping it in N you aren't wasting the energy from the battery but if you keep it in gear and use a bit of regen to maintain the normal cruising speed then you are storing that gravitational potential energy (GPE) for later. Also since you will never only go downhill you can look at GPE as another way for your car to store energy. For example I live just on the top of the Niagara escarpment. At the end of every day I'll climb it and store that energy in the car in the form of GPE then leave the next day with 22.6 kWh of available energy in the battery and a certain amount in GPE that I'll use in the first 5 miles of my drive. Repeat again and at the end of the day I'll take more out of the battery going up that hill to store and re use the next day. It makes the GOM even more worthless for my wife's drive who doesn't calculate this.

This all varies with the speeds that you get and the aero of the car so to say 1 is better than the other for all people on the internet is hard without data. You'll have to do your own data, ie how many gids do you have at the top then N coast all the way down and mark the point at which you return to the same speed you were at at the top. Gids should be the same or maybe a bit off due to accesories. Do it several times. Then do some runs with regen, mark the gids at the top, regen holding your speed at the bottom gids go up then when you reach the point at which your coasting would have got you back to the same speed note your gids and compare to the all coast runs.

minispeed said:

False when coming to a stop yes but if you aren't stopping and are going down a long grade at highway speeds followed by a level road then maybe true. If going down the long grade would get you up to a speed higher than your usual level cruising speed then the energy wasted to drag will grow.

The key point is to find when that extra drag energy lost at that higher speed is greater than the efficiency loss of using regen...

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As you suggest, it has to do with the length and/or steepness of the grade. In physics terms the limit is "terminal velocity", where the energy lost to drag equals the energy input from gravity, so all potential energy is being lost. Terminal velocity depends on air density and the grade (as well as rolling resistance).

Regen would always be preferable to traveling at terminal velocity. When traveling at speeds well below terminal velocity, coasting for a time can be more efficient than regen, although coasting up to terminal velocity is not. When reducing speed in ordinary conditions, such as coming to a stop, coasting is usually more efficient than regen.

Much of this is dependent on the efficiency of regen and we have had a number of debates about that figure. I'll guess 50%, although I don't think we ever pinned it down. If it is that low, coasting is going to be preferable to regen in most ordinary driving situations (where safe to do so, of course).


Since I drive hills and undulating terrain all the time, and rarely deal with traffic, I get to play with regen levels and coasting a lot. It's a game.

One of my routine situations is a reduction in speed limit from 60 mph to 50, on a mild upgrade. I just shift to neutral until my speed drops near 50 then shift back to D and reset cruise control. I do the same thing when the speed limit drops to 35 and 25 later on. At my altitude drag at 60 mph isn't very much but the drag+grade does gradually slow me down, while momentum keeps me moving forward with no energy input. The alternative, of course, is to quickly regen my way to the lower speed and then continue to draw energy from the battery over the (rather long) distance that I would otherwise have been coasting uphill.

jftuga said:

I was just wondering if when putting my 2015 Leaf in neutral when coasting down hill will I "hurt" the engine when putting it back into drive? For example, I may be going 50mph and then see a quarter-mile downward slope. I will put the car into 'N' and coast. I may speed up to 54mph. When the hill levels off, my speed will go back down to 50. At this point, I will switch the car back into "D".
I try to do this as many times as I can throughout a 60 mile trip.

I am just wondering if this has any kind of negative impact on the engine or the transmission.

Thanks,
-John

Click to expand...

This is my normal driving mode. In heavy traffic I may (and do) switch from drive to neutral to drive several times per minute

RegGuheert said:

TimLee said:

Don't get used to the quick into Neutral by shifting to Reverse.
You will forget and do it sometime at low speed and LEAF will try to come to abrupt halt.
I came close to being rear ended with that mistake one day.

Click to expand...

+1...Only I did it twice before I decided to give it up.

Click to expand...

I have done it several times and its actually quite effective for dealing with tailgaters

w4y said:

TickTock said:

Yup. Doesn't hurt anything... except your mileage. There is very little benefit to going into N on an EV. If you are coasting to slow down, it can be helpful to avoid regen. However, in the case you mentioned (going downhill, accelerating), you are actually going to end up using more energy with this practice since you allowed the car to speed up to 54 mph. Be better off leaving it in D and letting the regen maintain your 50 mph - then you are recovering the excess energy during your decent instead of burning it off in wind drag.

Click to expand...

This is false. It will actually HELP your range IF you coast to a complete stop without regen/braking. This means 100% of the momentum is being directly applied to the forward motion of your car, and not restored into the battery. The key is regen is not 100% efficient. Some amount of energy during regen is lost to heat, and hence avoiding regen is preferable for longer range.

However, you must not brake at all for this to be effective.

Click to expand...

You probably should actually read a post before stating it is false. My comment remains correct and yet doesn't contradict anything you stated (which is also correct).

When you need to continue moving, then coasting in neutral is the better way to go. Moving the vehicle forward with the kinetic energy, by coasting is the most efficient thing to do.

When you need to slow down, then regen is the best way to do that.

TickTock said:

w4y said:

TickTock said:

Yup. Doesn't hurt anything... except your mileage. There is very little benefit to going into N on an EV. If you are coasting to slow down, it can be helpful to avoid regen. However, in the case you mentioned (going downhill, accelerating), you are actually going to end up using more energy with this practice since you allowed the car to speed up to 54 mph. Be better off leaving it in D and letting the regen maintain your 50 mph - then you are recovering the excess energy during your decent instead of burning it off in wind drag.

Click to expand...

This is false. It will actually HELP your range IF you coast to a complete stop without regen/braking. This means 100% of the momentum is being directly applied to the forward motion of your car, and not restored into the battery. The key is regen is not 100% efficient. Some amount of energy during regen is lost to heat, and hence avoiding regen is preferable for longer range.

However, you must not brake at all for this to be effective.

Click to expand...

You probably should actually read a post before stating it is false. My comment remains correct and yet doesn't contradict anything you stated (which is also correct).

Click to expand...

You overestimate the efficiency of regen (Hint: It's not very efficient). There are plenty of anecdotal evidence (here, Tesla forums, etc) that suggests coasting during downhills is more efficient than regen in almost all cases.

In this case, coasting is the clear winner, as 54 vs 50 MPH does not increase drag coefficient very much (probably 5% more). Regen will be much lower than this.

NeilBlanchard said:

... When you need to slow down, then regen is the best way to do that.

Click to expand...

As dgpcolorado explained well, it depends.
In some slowing down situations using regeneration is more efficient.
In others it isn't.
Depends on the grade, the speed changes, and whether you are going downgrade or climbing.

w4y said:

You overestimate the efficiency of regen (Hint: It's not very efficient). There are plenty of anecdotal evidence (here, Tesla forums, etc) that suggests coasting during downhills is more efficient than regen in almost all cases.

In this case, coasting is the clear winner, as 54 vs 50 MPH does not increase drag coefficient very much (probably 5% more). Regen will be much lower than this.

Click to expand...

You can't look at Tesla results and compare them apples to apples with the leaf. With our much more brick like car we will reach a point where we are wasting more energy just moving air a lot earlier than they will. I do agree at 50 vs 54 mph it probably doesn't matter. I have 2 places where I'll drive down the Niagara Escarpment, 1 is long and flat speed limits 62 mph and I'll maintain about 65 in this weather, it will push to 70 when it's warm and will hold about 55 when it's cold. Another is much steeper with a 50 mph limit and the car will easily go over 70 in any weather. It's better there to use regen for overall energy efficency, and not just to avoid a speeding ticket.

Hi Tim,

TimLee said:

NeilBlanchard said:

... When you need to slow down, then regen is the best way to do that.

Click to expand...

As dgpcolorado explained well, it depends.
In some slowing down situations using regeneration is more efficient.
In others it isn't.
Depends on the grade, the speed changes, and whether you are going downgrade or climbing.

Click to expand...

Coasting is best when you need to carry speed, and regen is best when you need to slow down. Friction brakes are only for emergencies and the last few MPH when coming to a stop, when regen no longer works. If you come into a stop too hot, you have already wasted the energy, and you only heat up the brakes; which is a total waste.

I have been ecodriving for almost 7 years now, and I have the techniques down to habit, really. My best average on a charge so far is just under 217Wh/mile aka 4.6miles/kWh - measured from the wall and corrected the odometer, not the dash meter, which was 5.5miles/kWh. Now that the weather is getting warmer, I should be able to improve on that.

http://ecomodder.com/forum/em-fuel-log.php?vehicleid=8730