School me on my gear ratio

Discussion in 'Fuel Economy' started by Gageraid, Jan 9, 2015.

  1. Gageraid

    Gageraid Well-Known Member

    1st: 2.80
    2nd: 1.55.
    3rd: 1.00
    4th: 0.69

    In simple terms, how does each gear vary in mpg? I'm curious just how much mpg can vary in each gear before overdrive (4th gear).
    The transmission is an automatic 42rle in a 2008 Jeep Liberty.
  2. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    In short, the lower gears (higher number ratio = high rpm) give more power but worse mpg.

    Here are my testing results in my Fit. Your numbers will obviously be different but the pattern should be similar.
  3. RedylC94

    RedylC94 Well-Known Member

    That's right, assuming you're going equal road speeds under otherwise similar conditions in different gears.

    If we instead assume equal engine speeds, lower gears give lower road speed, higher possible torque to the wheels, equal power (which is essentially torque times speed), and worse mpg.
  4. Gageraid

    Gageraid Well-Known Member

    Any additional info you guys could give me on how my lower gears react to coasting?
    Trying to optimize my mpgs when my engine is still cold.
    Try to get out of first gear as soon as possible?
    Thank you so far!
  5. RedylC94

    RedylC94 Well-Known Member

    In general, yes. Accelerate moderately, then you can encourage automatic upshifts by briefly letting part-way off the accelerator.

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