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Slightly low MPG?

Discussion in 'Gen 3 Prius Fuel Economy' started by tortillachip48, Sep 7, 2020.

  1. tortillachip48

    tortillachip48 Junior Member

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    2014 Prius
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    Three
    I have a 2014 Prius III at 141,900 mi w/ Michelin Defender 15" tires at 42 psi.

    I typically see 50 MPG on the backroads - mild HVAC, modest acceleration, 55 MPH, etc. But today it was hot, I had AC on, going 70 MPH. I got 37 MPG for the first 7 mi (AC's still trying to reach setpoint) and 45 MPG after. Note: I use Eco mode, but I'll floor it to make a safe merge.

    Is that normal? I see people who are getting 50+ on the entire tank of mixed driving. Is it the high mileage or tires, or are these trips too short?

    I've cleaned the EGR, cleaned the MAF, changed the spark plugs, changed all air filters, changed ATF + coolant, run Lucas fuel system cleaner through the gas tank.
     
    #1 tortillachip48, Sep 7, 2020
    Last edited: Sep 7, 2020
  2. jimontheocean

    jimontheocean Member

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    I have a 2010 with 176k. Backroads, I get 51+,,,but as soon as I hit the interstates running 75-80, it drops off to about 48....I would guess thats normal.
    OEM wheels and lrr tires at 39psi.
    I did install an oil catch can, that's working great.
    Posted via the PriusChat mobile app.
     
    #2 jimontheocean, Sep 7, 2020
  3. bisco

    bisco cookie crumbler

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    yes, that is normal
     
    #3 bisco, Sep 7, 2020
  4. fuzzy1

    fuzzy1 Senior Member

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    Reduced MPG during engine warmup is to be expected. Add in the initial cooling load for a hot car, and MPG during that time will definitely be low.

    What matters is longer run MPG. And 45 MPG at 70 MPH is absolutely normal for a Gen3. In cooler weather with lower rolling resistance tires than those Defenders, about 50 MPG at that speed is the best you can expect. Higher mpg requires lower speeds.

    Defenders (I have them too) are not the best for MPG, but make up for that by being better all-around tires.

    P.S. This MPG-vs-MPH chart may be of interest:
    Updated MPG vs MPH chart | PriusChat
     
    #4 fuzzy1, Sep 7, 2020
  5. Grit

    Grit Senior Member

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    I currently have defenders myself, last week’s commute yielded 67 MPG with 530 miles driven, mdf screen posted in the “what ya did with yer prius today” thread on page 919 for the naysayers :LOL:
     
    #5 Grit, Sep 8, 2020
    RMB likes this.
  6. fuzzy1

    fuzzy1 Senior Member

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    When I was commuting in my 2010 Prius with OEM tires, mostly on stop-and-go surface streets and arterials but with some congested (i.e. below PSL) partial highway returns in the evening, I was often getting 72 MPG during the good weather season, peaking at 76 on my best days. 32 to 36 miles round trip, depending on which of numerous congested routes I chose. (The bicycle route was 34 miles RT, and much more pleasant.)

    My 2012 seemed to get its best MPG on the factory LRR tires, not on the subsequent Defenders.

    Your picture shows an 'average' speed of 39 MPH. BobW's MPG-vs-MPG chart shows that at that steady speed, the car is capable of 80 MPG indicated. A good Gen3 rule-of-thumb is that the car is capable of MPG+MPH = 120, under very good conditions.
     
    #6 fuzzy1, Sep 8, 2020
  7. tortillachip48

    tortillachip48 Junior Member

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    Three
    My record is 58 MPG - driving at night, no HVAC, 40 MPH with occasional stop lights, may have had a slight tailwind or downhill. :)

    Average on the tank is often around 47 MPG (calculated at the pump), but I take the 40-55 MPH streets whenever I can. (Moderate acceleration, coasting and minimizing braking.) I can usually meet or exceed EPA figures doing this on other cars. Are hybrids more sensitive to HVAC and outside temperatures?

    I do notice the battery drops quite a bit if I'm at a stop light, ICE off, AC full blast. I've heard of people using ScanGauge to measure the current draw (significant!) but I don't have that, just an ELM327. Torque Pro didn't seem to show much on the hybrid system, but did verify that coolant temperature reaches 195°F within 2 miles and stays constant afterwards. Brake rotors are cool after driving. So that's good.

    What am I gaining and what am I giving up with the Defenders? We get plenty of rain in the winter, maybe once or twice a year I'll drive in mild snow. I was concerned that Eco tires would compromise that.
     
    #7 tortillachip48, Sep 9, 2020
    Last edited: Sep 9, 2020
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