AT has better MPG than MT?

Discussion in 'General Motoring' started by Bucky, Jun 7, 2005.

  1. Bucky

    Bucky Guest

    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.

    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, Jun 7, 2005
  2. Bucky

    Guardsman Guest

    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.


    Top gear ratio?

    EX MT: 5th gear = 0.757, final drive = 4.41
    EX AT: 4th gear = 0.638, final drive = 4.36
    Guardsman, Jun 7, 2005
  3. Bucky

    Dave Guest

    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.
    Dave, Jun 7, 2005
  4. Bucky

    dold Guest

    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.
    dold, Jun 7, 2005
  5. Bucky

    dold Guest

    Oops, reading sideways... AT & MT both have 15" on the EX.
    dold, Jun 7, 2005
  6. Bucky

    TeGGeR® Guest

    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.
    TeGGeR®, Jun 8, 2005
  7. Bucky

    SoCalMike Guest

    CVTs generally are. they pick the most efficient engine speed and the
    belt drive tranny ratio compensates.
    SoCalMike, Jun 8, 2005
  8. Bucky

    dold Guest

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

    Right you are.
    dold, Jun 8, 2005
  9. Bucky

    jmattis Guest

    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

    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.
    jmattis, Jun 8, 2005
  10. Bucky

    Bucky Guest

    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)?
    Bucky, Jun 8, 2005
  11. Bucky

    Nightdude Guest

    From my experience, It's the other way around. AT usually runs lower @
    highway speeds.
    Nightdude, Jun 8, 2005
  12. Bucky

    Bucky Guest

    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?
    Bucky, Jun 9, 2005
  13. Bucky

    jmattis Guest

    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
    jmattis, Jun 9, 2005
  14. Bucky

    Bucky Guest

    Then he should just drive in 4th all the time.
    Bucky, Jun 9, 2005
  15. Bucky

    jmattis Guest

    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.
    jmattis, Jun 10, 2005
  16. Bucky

    SoCalMike Guest

    which would be... what? my CX is a 5spd, and only has 108hp. 5th gear is
    for freeway cruising. cool with me.
    SoCalMike, Jun 10, 2005
  17. Bucky

    jmattis Guest

    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. ;^)
    jmattis, Jun 10, 2005
  18. I wouldn't care if they would just make what I want.
    Gordon McGrew, Jun 10, 2005
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