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Cruise Control dropping my MPG?

Discussion in 'Gen 2 Prius Fuel Economy' started by Drunken_Monk, Mar 22, 2007.

  1. Drunken_Monk

    Drunken_Monk Junior Member

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    Im a new 07 owner and I was driving home from work today and decided to use the CC. After about 3 min of driving on flat road I turned it off because it was dropping my MPG to about 32. I could use the throttle and get closer to 49. Any ideas?.... :eek:
     
    #1 Drunken_Monk, Mar 22, 2007
  2. efusco

    efusco Moderator Emeritus
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    Don't pay too much attention to that instantaneous MPG. For me my instantaneous MPG shows either 20-30mpg or 99.9mpg and rarely anything inbetween for the way I drive my usual commute....that's what happens with a pulse & glide technique.

    On a flat road CC can be quite effective and, over time, get you better FE than you would with your foot trying to go a steady speed. On hilly terrain it is definately better/more efficient to turn CC off b/c it is overly aggressive in maintaining speed and will get you outside of the most efficient RPM range.
     
    #2 efusco, Mar 22, 2007
  3. Tom6850

    Tom6850 Retired

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    I agree with the good Dr. Set it and forget it on long drives, it has helped my trip mileage. Hilly or mountain driving I take it out of CC. I can do better and run much smoother with my foot.
     
    #3 Tom6850, Mar 22, 2007
  4. John in LB

    John in LB Life is good

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    There are many goals while driving, only one of which is optimizing gas mileage.

    Steady driving speed (good for your car and for all the other cars around you) and your comfort / convenience are certainly part of the equation.

    I use my cruise control - and just enjoy the drive / scenery.
     
    #4 John in LB, Mar 22, 2007
  5. JimboK

    JimboK One owner, low mileage

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    I'll take the others' comments a step further. I rarely use CC these days, even on the highway. To optimize fuel economy I pay close attention to keeping ICE RPM (monitored via my ScanGauge) out of inefficient ranges, low or high. Even small changes in incline can still lead to the CC pushing the ICE into those ranges, if only briefly. I would consider using it more if terrain was perfectly flat, but that's pretty rare in my neck of the woods.

    The one time I use it is on an extended highway trip (assuming some hills), and then only as a "safety valve" of sorts. I set it at what I think is the minimum safe speed for conditions. (For example, this past weekend I took a 2-hour trip, with CC set at 60 on a moderately busy highway with a 65 MPH limit.) Most of the time I am maintaining a faster speed with the pedal, continually adjusting pedal input, again, for ICE efficiency. On downhills I gain momentum (until I'm either unsafe or at risk for a ticket) to help get past the next uphill. But that momentum may be insufficient for a moderately steep or prolonged uphill. When the car slows to the CC's set speed, I let it take over until I crest the hill. A side benefit is that my right foot can take a short break from working the pedal.
     
    #5 JimboK, Mar 22, 2007
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