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Is coasting a new 2013 forester automatic transmission in neutral ok?

5K views 12 replies 12 participants last post by  Superacerc 
#1 ·
HI
I just bought my first Subaru Forester (2013 2.5x Premium) with an automatic transmission that has the sport shift mode. This is my first automatic transmission and my first AWD and I am having a hard time getting used to sub-optimal gas mileage (avg 16 mpg in city 22 hwy). Now, my car only has 1,500 miles on it so far and I am hoping this will improve once I continue to break the engine in. In the meantime, something I have been doing is shifting from "Drive" to "neutral" when i can coast (down hills, towards stopping, etc). I know it is minimal, but it does help with gas mileage.

My question is I am wondering if it is ok for me to shift from D to Neutral with this sort of car/transmission? I have always driven a manual and this was my driving habit with those, but I am not sure about it for this model/type of car. Thanks for any advice you can offer!!
 
#2 ·
Welcome to the forum. Fuel consumption should definitely improve with more miles, though don't expect miracles. Take heart that the Subaru has many other good traits which, my view, more than offset its thirst.

I don't know specifically about whether this neutral coasting is going to harm the transmission. From what I have read (not specific to Subaru) it shouldn't provided the engine is running to keep the lubrication flowing.

But are you sure it will save fuel? Read this for example...

Coasting in Neutral or Gear to Save Gas - Coasting and Fuel Economy - Popular Mechanics

Selecting neutral and switching the engine off at long red lights will probably make a bigger difference IMO.

-- Steve
 
#3 ·
no for many reasons:

at idle the fuel injectors are still "pumping" some gas into the engine. When rolling down the hill in gear, but foot off the gas pedal, the injectors are off.

When in neutral, the algorithm the trip computer uses is not based on how much fuel is actually consumed, but on some calculated value based on airflow past the mass airflow sensor, manifold vacuum and engine rpm.


Coasting in Neutral or Gear to Save Gas - Coasting and Fuel Economy - Popular Mechanics


additionally, with the transmission in neutral, the transmission's oil pump isn't being driven by the engine, so you have a gearbox turning over with no lubrication.

and finally its illegal in many states and jurisdictional due to not being in complete control of the vehicle.
 
#4 ·
Don't do it.

Rev matching, double clutching, synchros - NASIOC

To start with, it's illegal in most states to coast with the car in neutral. As noted in other threads on this topic, if you have a sudden need for power to maneuver it won't be there. (These laws were probably written long ago, when even normal cars, let alone big rigs, couldn't always make it down steep grades w/o smoking their brakes.)

Efficiency: in most fuel injected cars you'll waste gas - not save it - by going to neutral too soon, or by coasting in neutral. Why? In gear, with the throttle closed, fuel is usually cut entirely. Coasting in neutral? Engine is idling - which uses gas, and not very efficiently.
 
#5 ·
Hello and welcome to the forums from a little north of Seattle. I, like you just jumped into a 2013 premium as well though I searched out a manual 5 speed. I have around 700 miles on my odometer now and am averaging around 24 mpg combined city and highway. I drive pretty conservatively and don't want to abuse a brand new engine. I have only put ethanol-free gas in my Subaru and am hoping to start realizing better mpgs overall as more miles are put up on the clock.
 
#6 ·
Thank you all for your replies! I had not seen that pop. mechanics ad before and find it interesting to read. HA! I guess I had tricked myself into thinking I was saving gas on my manuals when I would do this.

As for the safety aspect of coasting in "n"- I do find it strange that it would be illegal to coast in neutral in some states. It does make sense if I needed to accelerate suddenly, but then again, that is where being a good and responsive driver is beneficial as well as not doing it in foolish conditions/situations!

At any rate, I really appreciate each of your feedback your tips on this. I love my new subaru and want to take the best care of it as possible! Thanks again
 
#7 ·
One of the problems with coasting with an AT is what do you do when you get to the bottom of the hill?

Shifting from neutral to drive in an AT while you car is going 40-50 mph can be quite stressful on the tranny. In effect the tranny has to go from idle mode to cruising speed real fast. That can be real hard.

I doubt there will be any appreciable savings in gas by coasting. Better off watching the right foot the other times.

And yes, your MPG will increase once you get it broken in. But the Foz is not a prius.

On my '11 limited I am averaging 25-27 mpg in stop and crawl traffic, when I first got the Foz, I was averaging just under 20.

But then I have a very light right foot. :biggrin:
 
#8 ·
You shouldnt coast in neural in a manual either... especially in a subaru..

Subarus have the distinct ability to restart a stopped (skidding) wheel with driveline input.. remove the driveline input and you actually reduce your ability to stop in a panic/low traction situation...

Ive taught myself to keep power going to the wheels right back down to the bottom of 2nd coming to a stop... usually this is almost stopped..

I know it doesnt really relate, but as stated above, in some states its actually considered "illegal"

Sent from an other planet
 
#9 ·
You should be able to do better than the mpg you are getting. Be very very easy on the throttle. Subaru's are (IMHO) very susceptible to bad mileage when using "too much accelerator" Mileage IMHO won't get any better. I have never seen increased gas mileage as a vehicle breaks in. Certainly not after 1000 miles. Thats over mega new vehicles.

Friggin Subaru is an aerodynamic brick.
 
#12 · (Edited)
Is there nothing in the owner's manual about the car moving while in "N"? Just curious, never owned an auto car that came with an owner's manual.

But yeah, it's very unsafe and is a horrible practice, both in an automatic and manual transmission car. This isn't a bicycle lol.

If you have a "live" gas mileage readout, watch it while you are coasting in gear with the foot off the gas -- it should show you that you aren't using any gas. Even my '99 5EAT Volvo's readout jumps to crazy high numbers when I'm going downhill with no throttle input and engine around 2K RPM.

Stan
 
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