Shifting into Neutral to improve gas mileage

toyota
gasoline
camry
transmissions
fuel-economy

#1

I have a '08 Toyota Solara V6 convertible with automatic transmission. The car gets pretty bad gas mileage (around 21 mpg combined). I would like to shift into neutral whenever it’s coasting downhill to improve the gas mileage (there seems to be a lot of engine drag when it’s coasting in Drive). Does constantly shifting in and out of Neutral harm the autotransmission?

(Note that this transmission does not have an explicit Overdrive button. It’s either Drive, or pushing the shift lever to the left you get into the semi-manual transmission mode, where you get to set the top gear to 1-4.)


#2

go to Actual Car Info…link on top of page…type in… shifting into neutral… and you will get all the past posts on this topic…


#3

Does constantly shifting in and out of Neutral harm the autotransmission?

the general consensus of this oft discussed idea is…the owners manual doesn’t recommend it for several reasons; it may not be safe, it may not be helpful to your goal, and it may increase wear.


#4

Chances are a 2008 car is going to get better mileage by leaving it in gear. Most modern engines (auto or manual) will turn off the fuel totally, when the car is moving fast enough to turn the engine over faster than idle. That it totally free miles.

You could gain a little more by taking it out of gear when the car slows enough that the computer starts sending fuel to the engine to keep it at idle speed. However very little fuel is likely to be saved and considering the cost of transmission, I would leave the car in gear as the transmission was designed.


#5

Yup!
This topic has been beaten to death over the past couple of years.
Suffice it to say that shifting into neutral in order to coast is NOT a good idea, either from an economy standpoint, or from a safety standpoint, and it is not really good for your transmission to do this either.

If you want to read the HUGE amount that has been written on this topic, use the “search” function at the top of the page.


#6

21MPG is “pretty bad gas mileage”? That’s pretty frugal IMHO. But anyway, do not shift into neutral, it’s illegal and you’ll just use more gas anway since when you take your foot off the gas whilst in drive and the fuel injectors are cut off. When in neutral they are still sending fuel to the cylinders since the engine will be idling.


#7

A Lotus Evora with the same Toyota engine manages 31 mpg on the highway. Neutral doesn’t save gas. When I am stuck in LA rush hour traffic, I keep my stick in 1st or 2nd 50% of the time with my engine screaming and still manage highway mileage. Neutral is not the answer, anticipating slow downs and avoiding the brake pedal is the key.


#8

meh, the Evora doesn’t bring much to the table IMHO. The value isn’t there, it’s an $80k car that doesn’t offer much in the way of straight line speed, its heavy for a Lotus, from what I’ve read it’s handling is good but not the best within its class. I’d rather have a Corvette Z06 that comes close to matching it for fuel economy, but also far faster. If it has to be a british car then then it makes sense to pony up the extra cash for a Noble.


#9

I’d be willing to bet that that new of a vehicle has one of those onboard fuel mileage readouts. Try coasting in gear, then coast in neutral, see if it changes any. Then, while someone comes speeding up behind you and you want to speed up, hit the gas while in gear and neutral, see what happens THEN.


#10

The fact that modern cars cut off fuel in certain conditions does not necessarily mean that shifting into neutral wouldn’t save gas.

First, fuel cut-off only happens in certain conditions, not necessarily whenever you’d like it to. I bought a ScanGuage for my '98 Contour, and found that–while it was good about cutting power at >55mph coasting, it was really bad about cutting power while, say, descending a hill in a low gear.

Just 'cause it CAN cut off fuel doesn’t mean it IS.

Second, it takes energy (in the form of car momentum) to “freewheel” the engine, even with the fuel off. In fact, it takes slightly more momentum to freewheel the engine without fuel going into the engine. This means that coasting in gear will always give lower FE than “shutting down in neutral.”

Given the right conditions (mostly relating to idle RPM much lower than in-gear RPM), it can consume more energy in fuel cut-off (in terms of momentum that must be re-built with gasoline) than to “feed the engine” at idle RPM in neutral.


#11

Waaaay back as this subject began its incessant, repetitious, ( did I mention redundant ) life cycle, I did myself a test.

Driving down the hiway at any speed, if I put it in neutral, the RPMs do not reduce to idle speed…
DO NOT reduce to to idle RPMs AT ALL.

At first the RPM drops a bit as if, but then the computer takes over and brings it back to near the RPM for that speed.
RPMs will only drop in neutral if I slow my MPH as well.

The computer knows, both in my 92 and 08, that when I am to engage drive gear once again, those RPMs will be needed.

If it actually went down to idle in neutral at 70mph…
can you immagine what would happen if you simply threw it in drive ??


#12

What you experienced isn’t necessarily true for all cars. On my Bronco the RPMs will go to idle a few seconds after shifting into neutral at speed. My 1992 T-Bird SC did the same thing. My mom’s Volvo does not however.


#13

The economy of gas will be marginal, also it is a very risky thing to do to shift between Neutral and Drive above 10mph (the “R” is so close :-/)
If you want to save gas mileage, you’d rather do a few simple things such as drive a constant speed as much a possible (if you have to break hard, the chances you did accelerate too much just before are very high!), don’t leave the engine on when parked, …
hope it helps!