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Cruise control and fuel economy

Discussion in 'Gen 4 Prius Technical Discussion' started by dangrass, Aug 4, 2016.

  1. Autoist

    Autoist Member

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    The car doesn't seem to apply brakes when CC is engaged going down hill, only "engine braking" to keep at the speed set, no fuel usage.
     
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  2. CR94

    CR94 Senior Member

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    Right, if you don't needlessly brake (whether friction, regenerative, or "B" type) on the downhill, you'll get a little farther beyond the downhill before needing to burn fuel.
     
  3. econo-one

    econo-one Junior Member

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    I have a scan gauge on my 2016 Prius and it definitely shows fuel consumption when going downhill with the engine spinning. The fuel gauge on the dash may be pegged at 150 mpg, but the scan gauge show gas mileage at somewhere between 50 and 100 mpg. So it appears that fuel is being sent to the engine. This is a shame, because engine braking is so minimal going down long grades after the traction battery becomes fully charged. I find that even putting the transmission in "B", the engine spins faster, but any additional compression braking is minimal--barely noticeable. Thus on long downgrades I end up using the brakes far more than I'd like.
     
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  4. tzx4

    tzx4 Active Member

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    That is my experience too. My former Prius c behaved differently. It would fill the battery, and then spin up the motor on long descents. The '16 Prius, not. Considering that my 550 pound heavier '16 is getting overall average 63 MPG is 6PMG better than the c, it is obvious that Toyota engineers know what they are doing.
     
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  5. That_Prius_Car

    That_Prius_Car Austin Kinser

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    Location:
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    Vehicle:
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    Two
    I did the same with my 2016. Driving to Pittsburgh the other day, I engaged cruise control and noticed it would not go into EV. Even on slight downgrades where it's not braking, but just giving a little bit of throttle, it spun the engine, so I turned off the cruise in favor of the engine not spinning and using any oil life.