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  1. #1
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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. Reputation: Yes | 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.
    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale: http://www.boostaddict.com/showthrea...r-kit-for-sale

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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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    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.
    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale: http://www.boostaddict.com/showthrea...r-kit-for-sale

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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.
    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale: http://www.boostaddict.com/showthrea...r-kit-for-sale

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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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