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    Fuel consumption - any advantage of longer 6th gear with AT?

    Hi guys,
    i just wonder if there is any advantage in fuel consumption with AT compared to MT while crusing around 60-90Mph. We know AT has really long 6th gear, but is there really a difference?
    Has anyone a few numbers for me?

    Greets from Germany

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    1 out of 1 members liked this post. Yes Reputation No
    I'd think it would be very minimal. On my last 300 mile trip, I got 30 mpg cruising 75-80, and 29.4 cruising at 90 on the way back in my 6at. Probably the same difference as driving with vs into the wind.

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    If the gear is longer and rpm's are lower, don't see why there would not be a minor benefit.
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    For a 2007 335i, the Official EPA MPG numbers are
    20-29 for 6AT
    19-28 for MT

    but if you have the 7AT, then its lower
    18-25 estimate

    http://www.fueleconomy.gov/feg/findacar.htm

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    Yes Reputation No
    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    If the gear is longer and rpm's are lower, don't see why there would not be a minor benefit.
    But how big is the difference really? Nobody testet average MPG at desired speed with cruise control?

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    Click here to enlarge Originally Posted by fischergeiz Click here to enlarge
    But how big is the difference really? Nobody testet average MPG at desired speed with cruise control?
    Well, I don't really know the difference on the 335. On the M3, I believe the M3 is rated 1 MPG higher with the DCT than the manual due to the 7th gear.
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    Im not interested official numbers. Real-world data are not the same. This is why i asked for selfexpierenced numbers

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    here are my observed numbers in a 300 KM trip with equal conditions.
    08 MT X3 : 22.3 MPG , 2900 RPM @ 65mph
    07 AT X3 : 23.1 MPG , 2350 RPM @ 65mph
    both cars were in a great condition.

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    Great, thanks ! That was the difference i expected.

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    Click here to enlarge Originally Posted by fischergeiz Click here to enlarge
    Im not interested official numbers. Real-world data are not the same. This is why i asked for selfexpierenced numbers
    Ok, good luck getting reputable numbers in test conditions that won't vary all over the place then.
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    with the 7 speed on the 335 there might be more tranny resistance... i always got around 30-32 mpg cruising 75-80
    JB4LIFE

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    ...and my manual seems to get around 29 when cruising on the highway. Maybe the lower RPM (automatic) does help a touch.

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    This is the point i dont know. Is the benefit of longer 6.gear with AT greater than the higher resistance compared to MT (if there is a more resistance at all)?

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    Click here to enlarge Originally Posted by fischergeiz Click here to enlarge
    Great, thanks ! That was the difference i expected.
    my pleasure sir Click here to enlarge

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