Terrible fuel economy

Discussion in 'Gen 3 Prius Fuel Economy' started by Joel W, Nov 26, 2016.

  1. Joel W

    Joel W New Member

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    First off, I deeply apologize if this is not in the right section. I checked around and I think it's this, but if it's not, please let me know and I'll re-post/delete this threat, etc...

    I have a 2011 Prius IV. It's been an amazing car and I love it, but I've never, EVER gotten over 48 MPG. I've changed driving styles, watched youtube clips, read these forums, and nothing - nothing - has gotten me to 51. Furthermore, my average is 45/46 at best. I don't live in a hilly area, and I take different routes to and from work all the time, each has a unique set of ups and downs, so my actual terrain isn't in question. Finally, I've had this car since June, so I've seen spring weather, hot weather, fall weather, and now cold weather. Nothing changes.

    I did the system diagnostic test, just now, in my car. My batter is at 11.5v. Not really sure if that's important (I think it's in the safe range), but after I did this, I turned me car on and checked my phone. My batter had about 3 or 4 bars, and that's when it happened.

    My MPG up until that point was 48.8 MPG. Impressive! In a matter of SECONDS, it went down to 48.4. Then, 48.1. I can't make this up: in a minute and a half, with me still parked, it dropped to 45.5MPG. I haven't even moved the car!

    As I drove off - and this is the case whenever I drive, for the first 5 minutes - the car registered about 30MPG in BATTERY mode (I apologize for not knowing the actual terms, but I'm talking about that rectangle that shows battery on the left side, gas on the right, power all the way to the right. I stayed on the left side and this was my MPG after I took my foot off the gas and let the car coast - that's right, it got less than 40MPG while it was COASTING).

    I can typically get 100+MPG if I'm driving on battery mode (left side of the rectangle), but only if the car has been on for a while. It always, always, always does this, no matter how charged the battery is.

    Is this normal? I'm okay with 46MPG, but on these forums and others all I see are people posting about getting 50MPG - really? Seriously?

    2011 vehicle, purchased used by a reputable dealership at 33k miles. They provide a warranty and I've taken it for all scheduled maintenance work/oil changes/etc. No red flags anywhere. And yes, I drive in ECO mode wherever I go.

    Please tell me if I'm doing anything wrong, or if this is just the way it is.
     
  2. bisco

    bisco cookie crumbler

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    welcome!
    11.5 is almost dead.:) was the engine running while the mpg's were dropping?
    if you're showing mpg's on the analog scale, the engine is running, even if you're in the left side of the rectangle. (hsi hybrid system indicator)
    100 mpg means the engine is off. if you were fully warmed up, your engine is probably running to charge the hybrid battery, which in turn is trying to charge the bad 12v battery.
    once you sort out your 12v, if your mpg is still low, we can try some other things. but in the end, a lot of people get in the 40's only.
    other things to check: tyre brand and model, inflation pressure. oil level and air filter.
     
    #2 bisco, Nov 26, 2016
    Last edited: Nov 26, 2016
    Mendel Leisk likes this.
  3. Joel W

    Joel W New Member

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    Yes, the engine was running while this was dropping. Is it the battery for the car (the $150 one), or for the hybrid ($2000+ one)? Again, I'm painfully ignorant to these terms, but it would help clarify...

     
  4. bisco

    bisco cookie crumbler

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    the $150. one. see my edit above. you can try charging it, but if it won't stay above 12.3 or so, you'll have to replace it.
     
  5. Joel W

    Joel W New Member

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    Got it, thank you, seriously. If this was the cause, how much of a difference would it make MPG-wise? 1 or 2 more?
     
  6. bisco

    bisco cookie crumbler

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    maybe, there have been reports of different amounts. sometimes it's just a lower voltage, but other times it's a bad cell inside the battery, causing the engine to run quite a bit more than necessary.
    on top of that, if it's really 11.5 with no load, you're going to get stranded eventually.
     
  7. Vman455

    Vman455 Senior Member

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    OK, you're freaking out because the car was still warming up. It won't turn the engine off until coolant temperature reaches 101F. If you want to see high tank averages, you need to take longer trips--long enough for a) the coolant and, more importantly, crankcase oil to get up to operating temperature (20-30 minutes with engine running), and b) drive it long enough after that to make up for the low mileage while the car is warming up. If your regular trips are only a couple miles, you'll only get mileage in the 40s or even 30s, especially as the weather gets colder, no matter how you drive.

    Also, anytime a car idles without moving, MPG will drop precipitously.

    Try taking longer trips; see if you can find someone local to ride along with and see how they drive; keep experimenting with your driving style. Go to an event like the Green Grand Prix and observe/learn as much as you can. There are lots of people out there who know how to drive efficiently, and they're usually not hesitant to talk about how they do it.
     
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