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Are you guys extremely light on the pedal?

Discussion in 'Gen 2 Prius Fuel Economy' started by rogerchin, Jul 15, 2024.

  1. rogerchin

    rogerchin New Member

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    I just recently purchased a used 2008 Prius. I noticed my regular driving habit is around 7.5 L/100km, that's about 31mpg. The previous owner got the average to 5.5ish L/100km after driving about 500km.

    Then I discovered that I can coast just using the electric motor by being very light on the peddle, not enabling the engine to do its thing unless necessary. My previous car was a 2011 accord v6, so this fuel economy is a new thing to me and feels super awkward when I'm starting off at a red light like a granny.

    Is this how we're supposed to drive to save gas? When on straight road, use electric motor. When on downhill, foot off the peddle. Only use engine when absolutely necessary, like going up hill.
     
    #1 rogerchin, Jul 15, 2024
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    "Pulse and Glide" is the technique that you want to learn.

    This is where you accelerate moderately (pulse) such that you're using the engine at its efficient rpm to accelerate the car, then once up to speed, you lift off, let the engine shut off then lightly press on the accelerator (glide) such that you're neither using engine power nor battery power (essentially, like being in neutral on a bicycle and not pedalling). This is how you maximise the efficiency of each side of the powertrain.

    If you use the battery, eventually it'll need to be charged either via the engine or going downhill so you want to use as little as possible to stretch the battery charge. And when you use the engine, you want to use it such that it revs to the optimal rpm range to maximise its fuel usage vs. power output. If you accelerate too hard, then you're either using too much fuel (obviously) or the computer may choose a different rpm than optimal and either use the battery to supplement power or over produce power and send the excess into the battery to charge it (which will incur charging losses... gas tank to engine to elec. motor to battery and then elec. motor to wheels. Ideally, you'd want gas tank to engine to wheel or gas tank to engine to elec. motor to wheel).
     
    #2 Tideland Prius, Jul 15, 2024
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  3. dolj

    dolj Senior Member

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    No, don't do this, you'll just p155 people off. Accelerate at 14 - 12 L/100 km (or more as required) get up to speed relatively quickly and then worry about eco-driving.
    Probably will not be possible to do this unless you're also going downhill or slower than 40 km/h.
    You're trying too hard. Just drive the car normally using normal eco-techniques,

    Like Tideland Prius said learn the pulse and glide technique and make sure your tires are inflated to 240 kPa on the front and 230 kPa on the rear.
     
    #3 dolj, Jul 16, 2024
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  4. bisco

    bisco cookie crumbler

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    Congrats and welcome!
    Keep in mind that you’re driving an old car that may not be capable of achieving expected mileage.
     
    #4 bisco, Jul 16, 2024
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  5. TMR-JWAP

    TMR-JWAP Senior Member

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    Regardless of anything said in this thread, if you're getting 31 mpg, there is something wrong with the car.
    NORMAL driving, as if it was any other ICE car should result in 44-46 mpg. Blasting the AC while doing that will likely drop it to 41-45 mpg.
    85+mph continuous on a highway trip should be in the 36-39mpg range.

    When my son used my 2007 for driving to work, 5 minutes each way, the car rarely ever got out of warm-up mode and still sat at 38 mpg at the end of a tank. If I used the same car for my work commute, ~21-23 miles each way (~60 mph avg between 40 and 65mph zones) depending on exact route, I easily get 50+mpg.

    31 mpg? Something is broken.
     
    #5 TMR-JWAP, Jul 16, 2024
  6. rjparker

    rjparker Tu Humilde Sirviente

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    You are overthinking this and even pulse and glide is not needed to get 45-50 mpg. In the early days techniques like pulse and glide, drafting close behind trucks or driving without AC or heat was sometimes used by “hypermilers” to get ridiculous mpg like 60-70mpg.

    On the other hand, old hybrid batteries can reduce mpg by 5-10 mpg since they do not have much regen storage capacity left, the real hybrid mpg technique. Braking late and hard negates regen; so the soft pedal you need is the brake pedal. Driving short distances exclusively hurts mpg as efficiency is less while warming up. Driving over the speed limit hurts; 75-85 mph really hurts.

    Less likely are dragging brakes or a 12v battery so bad it sucks up 60 or more amps continuously. Both are rare.
     
    #6 rjparker, Jul 16, 2024
  7. rogerchin

    rogerchin New Member

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    The MFD reads 7.5 litres average but after filling my tank and dividing by 407km, I got 9 litres/100km which is pretty bad but still better than my accord. That was my first tank of gas after the purchase, I'm on my second tank now and doing the pulse and glide technique. So far, it looks like its getting better because the first tank, after about 35km, the first bar was gone. Now the first bar is still there and I'm at 70km.
     
    #7 rogerchin, Jul 18, 2024
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