AT has better MPG than MT?

I was checking out the MPG, and I noticed that for the 2005 Civic EX
Special Edition, the AT has better highway gas mileage than the MT (38
vs 37). I can understand them being the same, but how can AT be higher
than MT? The AT even weighs 56 lbs more.

http://automobiles.honda.com/models/specifications_full_specs.asp?ModelName=Civic+Sedan&Category=ALL

Is this just a deviation error in the EPA test? Is the EPA test a
one-shot deal, or do they conduct it many times and take the
best/average? Perhaps due to slight statistical deviation, maybe AT got
37.50 and MT got 37.49. Round it to the whole number and it looks like
a big difference.

 

Bucky writes:

b> I was checking out the MPG, and I noticed that for the 2005 Civic EX
b> Special Edition, the AT has better highway gas mileage than the MT (38
b> vs 37). I can understand them being the same, but how can AT be higher
b> than MT? The AT even weighs 56 lbs more.

b> http://automobiles.honda.com/models/specifications_full_specs.asp?ModelName=Civic+Sedan&Category=ALL

Top gear ratio?

http://www.hondanews.com/CatID2015?mid=2004091342203&mime=asc

EX MT: 5th gear = 0.757, final drive = 4.41
EX AT: 4th gear = 0.638, final drive = 4.36
--

 

Looks like a good call to me. Guess with the torque
multiplication of an auto, and the automatic kick-down, they feel
they can get by with a taller ratio. And maybe an aggressive
lockup control algorithm which will make the auto a lot more
efficient than otherwise. Still seems unusual to best a manual on
the EPA highway drive.

 

And 15" wheels instead of 14". Taller overall?
Lower city mileage, which would also fit with the "taller" idea.

My Civic Hybrid has CVT, not a four speed AT, and I can believe that it is
much more efficient at selecting engine speeds than I would be with a MT.

 

Oops, reading sideways... AT & MT both have 15" on the EX.

 

Unlikely. That would alter the ride height unless the suspension was made
differently, which it's surely not.

If you look at the tires, I think you'll find the height percentage will be
different between the two. The 15" wheels will have a smaller number there.
i.e.: 195/65-14 vs 195/55-15. Something like that.

 

CVTs generally are. they pick the most efficient engine speed and the
belt drive tranny ratio compensates.

 

Tire Diameter Tread Width
185/70R14 24.25 5.51
195/60R15 24.21 6.25

Right you are.

 

how can AT be higher

Yes, its in the gearing. My '96 Infiniti I30t automatic is rated for
28 highway. Less than 10% of those I30's were manuals, rated at 26
mpg.

4-speed Automatic: 0-60 8.2 sec
5-speed Manual: 0-60 7.5 sec

There was a car back in the early '80's that even accelerated slightly
better with a 3-speed auto than a 5-speed manual, a Ford compact I
think. Tinkering with converter stall speeds and other auto tranny
items can make them pretty effective competition.

 

EX MT: 5th gear = 0.757, final drive = 4.41

So the top gear ratios are:
MT = 0.757 x 4.41 = 3.34
AT = 0.638 x 4.36 = 2.78

Does this mean that if a MT is going at 3000 rpm,
then the AT is only going at 2497 rpm??? I thought that AT ran at
higher rpms at highway speeds (or was that a thing of the past)?

 

From my experience, It's the other way around. AT usually runs lower @
highway speeds.

 

I guess I had the wrong impression. I always figured having the extra
gear with a manual meant the lowest gear could be lower and the highest
gear could be higher.

I don't see why they don't make the top gear ratio in MT be equal to
(or even smaller than) AT. The MT driver would just downshift to 4th
before trying to accelerate at highway speeds. Isn't that the point of
MT, so that the driver can decide what gear they want to use?

 

I think you have the right impression overall. But, it is not
universally applicable. The driver of a sporty car sure doesn't want
to have to downshift to 4th, to climb a little hill or do a lazy
passing manuever. It's a sure sign of an econobox when you floor it in
5th and nothing happens. Even some econoboxes are designed to avoid
this.

 

Then he should just drive in 4th all the time.

 

As a person who's not especially fond of manual transmissions, I could
agree with you. But, in the marketplace, manufacturers will instead
respond by selling these drivers what they want in the first place.

 

which would be... what? my CX is a 5spd, and only has 108hp. 5th gear is
for freeway cruising. cool with me.

 

Which would be, maybe a Corvette. Maybe a Viper. Maybe an I30 or
Maxima SE with a 5 speed. I haven't driven one, but I suspect even a
6-speed V6 Accord coupe might pass the test in most people's eyes.

I see what's going on here. I'm in a den full of manual transmission
mavens, and said something nice about automatics. ;^)

 

I wouldn't care if they would just make what I want.