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Thread: Why is the 1-series' gas mileage worse than the 3-series coupe?

  1. #1
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    Why is the 1-series' gas mileage worse than the 3-series coupe?

    Sorry if this has already been addressed, but why is the 128i's gas mileage less than the 328i coupe's (the same is true of the 135i and the 335i coupe)? Here's a cut & paste from the BMWUSA's site comparing the two cars with the 128i on the left, and the 328i on the right:
    Fuel economy city 18mpg 20mpg
    Fuel economy highway 28mpg 30mpg
    Fuel tank capacity 14.0 gal. 15.9 gal.
    The 128i has the same engine, very similar tires (both 17"), the same transmission, and it weighs 100 pounds less. I can't believe the engineers would design it in such a matter that the aerodynamics would be so much worse as to account for the difference. And the city mileage of the 128i is even less than the published 335i coupe's (18 versus 19)!

    On the surface it makes no sense.

  2. #2
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    When I look up the ratings for the 1 series at bmwusa.com, all I can find is "TBD". Where did you find them?
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  3. #3
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    Quote Originally Posted by m3bs View Post
    When I look up the ratings for the 1 series at bmwusa.com, all I can find is "TBD". Where did you find them?
    From this link. Its from the "Compare Vehicles" function from the 128i portion of the BMWUSA site. On the scroll down menu entitled "Compare to another BMW" select "2008 328i Coupe," then click the "Compare" link. Once it opens click the plus ("+") sign to the right of "Power & Performance." Within "Power & Performance" you'll find the "Fuel Economy" section.

  4. #4
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    Perhaps the EPA testers couldn't resist the temptation to nail it!
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    THe 1 series is a higher car. Might be because it has more drag.

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    Sounds like a good argument for lowering springs.
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    My guess would be the final drive gearing is lower on the 1 due to its more performance nature than the 3.

    EDIT: Never mind I stand corrected the rear gear on the MT is 3.08:1 for both the 3 and the 1.


    the coefficient of drag is slightly higher on the 1 that the 3
    "1"=.33 and the "3"=.30 so that is the big thing, the bit of extra drag at higher speeds is your mileage killer also negates the weight saving on long stright high speed runs with the 335i
    Last edited by sleeve; 04-28-2008 at 02:58 AM.

  8. #8
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    The 3 series numbers were probably based on the old EPA mileage rating and the 135 on the newer, more realistic rating.
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  9. #9
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    Quote Originally Posted by sleeve View Post
    My guess would be the final drive gearing is lower on the 1 due to its more performance nature than the 3.

    EDIT: Never mind I stand corrected the rear gear on the MT is 3.08:1 for both the 3 and the 1.


    the coefficient of drag is slightly higher on the 1 that the 3
    "1"=.33 and the "3"=.30 so that is the big thing, the bit of extra drag at higher speeds is your mileage killer also negates the weight saving on long stright high speed runs with the 335i
    Quote Originally Posted by aus View Post
    The 3 series numbers were probably based on the old EPA mileage rating and the 135 on the newer, more realistic rating.
    My vote goes for being a split between these two.

  10. #10
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    I'm counting on getting 30 out of mine.
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  11. #11
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    Drag coefficient would have negligible effect on city driving. And the newer 3-series should also be rated using the new EPA ratings.

    Maybe the tires are different and there is greater rolling resistance on the 1-series' rubber?

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    Quote Originally Posted by 1er View Post
    Maybe the tires are different and there is greater rolling resistance on the 1-series' rubber?
    If the 1 serie is indeed $10k less than a 3 serie, then I am sure the quality of the tires has suffered. Therefore, probably cheaper tires with more rolling resistance.
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    Quote Originally Posted by Massive Lee View Post
    If the 1 serie is indeed $10k less than a 3 serie, then I am sure the quality of the tires has suffered. Therefore, probably cheaper tires with more rolling resistance.

    could you get better tires in hopes of getting better gas mileage?

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    Quote Originally Posted by KClarkBMW View Post
    could you get better tires in hopes of getting better gas mileage?
    Yes. The rolling resistance is another facet of tire design. Also, improperly aligned or under inflated tires will affect mileage.
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    great. i am thinking about getting a 1 series, itll be my first BMW, and i am pretty clueless. what type of tires do you recommend?

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