I have been the owner of a 5 speed for 1 year and just recently switched to a A/T. I want to get the best mileage I can out of this thing and I was wondering if it is a problem to put the tranny into neutral when coasting to a stop or at a red light.

Sorry if this has been covered already, there is just so much information on this website I figured someone could just give me a quick answer.

Secondly, I wanted to know if resetting the ECU would help mileage.

I just got the car and it seems to only be getting around 30 mpg for the last 180 (highway) miles.

Thanks!

 

the car does not save any gas when it's idling in neutral while you
approach a stop. just keep it in gear and let it downshift on its own.

when the car comes to a stop or near stop, shift into neutral. even
shut the car down if you're waiting for a freight train to pass or
something that'll take longer than a normal stop.

resetting the ECU will not improve milage....rather it will in most cases
make your mpg worse until it re-adapts to your driving inputs and
environment. brand new cars usually have bad mpg because one of
the reasons is the ECU has not adapted to the working environment.

 

I would echo kenchan's comments. I think that coasting down in gear may actually give you better economy due to the deceleration fuel cutoff that only occurs if you coast in gear. I would also add that it's probably not a good thing to put an AT car in neutral and coast with the engine off for long periods due to the fact that the engine would no longer be turning the fluid pump in the AT that lubricates the transmission.

 

do not do any extra "shifting" with your automatic. it will shorten the life of your automatic transmission.

 

Ask a user with a SG. It should be easy to READ what the GPH is in drive and neutral

 

I have an SG and I've done a few tanks worth of testing the shifting to neutral at stop lights as well as shifting to neutral to coast down hills ideas.

Shifting to neutral at stop lights does absolutely nothing since the RPMs in neutral are the exact same as they are in gear while stopped. The SG confirms by showing 0.2 GPH both in neutral and in gear while stopped.

Shifting to neutral to coast down hills, while illegal and most likely very bad for your transmission, does increase mileage significantly. By shifting to neutral down hills on my way home I saw an increase from 37-39 mpg (a large part of my trip is highway) to 42-43 mpg. This is because the engine only runs at the idling speed of ~740 RPMs while the car is still moving at 40 MPH. The difference in the scanguage reading (the realtime one that changes every second or so and doesn't really effectively tell you how you're doing for the tank) shows a big difference. I get 78-120 MPG coasting in gear down a hill at 40 MPH, on the same hill at 40 MPH in neutral the SG shows 300+ MPG.

Please don't yell at me for using the realtime MPG gauge all you SG guys. I only used it to prove a point that coasting in neutral is actually more efficient than coasting in gear. I use the Current Average and Tank Averages for any real numbers such as the 37-39 and 42-43 MPG for the standard and neutral shift tanks averages.

Once again I would like to say that I can't recommend ever doing the neutral shift as it is highly illegal and if you get in a wreck and your car is found to have been in neutral all fault will automatically be placed on you. Not to mention that it will kill your transmission over time.

 

Your first mistake was switching to AT. The AT Fits get worse city MPG, and only slightly better highway mileage. If your commute has lots of highway travel, then getting the AT was probably a good choice. Otherwise, you should have stayed with the MT if you wanna squeeze great MPG.

 

i dont see how the AT would get better fuel economy on the highway. the RPM is lower? but you must push the pedal more to go the same speed as a MT.

i have been getting 55ish trips in my MT. i dont think an AT could get close to that lol

 

I've been driving stick for the past year and got 21 mpg. If I can get a new car and not have to mess with a clutch and STILL get more MPG than my old car I'll take it. I didn't choose the car because of the transmission, I chose it because I liked it.

Point of thread: Wondering about how a AT works. NOT debating AT v MT

 

I'm curious. What're you cruising at to get 55mpg?

An AT and MT work in completely different ways to achieve the same end. Shifting to N in an AT isn't going to net any MPG gains like it would in a MT. An AT works with planetary gears and various clutches and bands that are activated hydraulicly.

 

55-65mph. depending if im going down hill or not

 

I have noticed that the GPH is higher with the headlights on, like 0.3 vs. 0.2. Shifting into neutral at a stop when you're running the headlights will lower the GPH from 0.3 to around 0.24. Not much, but could add up to a few tenths of a MPG over the course of a tankful.