Lower than expected gas mileage?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Jordan.luna, Oct 21, 2019.

  1. Jordan.luna

    Jordan.luna New Member

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    I have a 2008 Prius and have never seen the average mpg above 44. I suspect there is a cooling system issue because the heat is not always consistent and turns off if I stop the car or the engine turns off. It’s almost like the battery can’t support the heat being on? That probably sounds really dumb but I don’t know how else to put it. Today the red triangle came on for about 5 seconds when driving but went off. No other indicator lights. Any suggestions on what the issues could be? Not sure if they’re possibly connected or not.
     
  2. bisco

    bisco cookie crumbler

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    44 isn't out of the ordinary.check the coolant level

    check the oil level

    if the triangle came on, there should be a trouble code stored

    how many miles on her?
     
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  3. Jordan.luna

    Jordan.luna New Member

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    I did just get the oil changed. I also added some coolant a few days ago but haven’t checked since. 132k miles. I should get the codes red but I’m a little scared of what I’ll see. The hybrid battery seems to be in good shape from what I can tell. I don’t have much Prius knowledge so I don’t know for sure
     
  4. fuzzy1

    fuzzy1 Senior Member

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    Excluding old car problems, start here for the things that affect new cars too:
    Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new

    One significant thing missing from that list is brake drag.

    For learning how to drive for good MPG, start here:
    New owner? Want MPG help? Read this first. | PriusChat

    How long have you had this car? The above links don't address old-car isssues, such as the red triangle. Other folks here can chime in on those issues.

    ============
    PS. As Bisco said, 44 MPG is not abnormal for your vintage, especially without knowing more details of your driving pattern. The 50 MPG advertising began with the 2010 model year.

    Here is the spread that other drivers reported to the EPA:

    prius2008_epa.JPG
     
    #4 fuzzy1, Oct 21, 2019
    Last edited: Oct 21, 2019
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  5. Jordan.luna

    Jordan.luna New Member

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    This is helpful because maybe I was having unrealistic gas mileage expectations. I have had the car for less than a month now. I’m in Atlanta so my driving varies from suburban hilly areas to highways to heavy city traffic. I try to coast as much as possible and I feel like that has helped a lot.
     
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  6. fuzzy1

    fuzzy1 Senior Member

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    ^ Just in case you haven't seen it elsewhere yet:

    Note that for best 'coasting', don't take your foot completely off the gas pedal, as this will cause a little bit of regeneration drag, intentionally designed in to give it a little more of the driving feel and controlability of a traditional non-hybrid.

    Instead, keep a bit of light pressure on the pedal, just so that the power flow arrows disappear on the engine / battery / electric-motor display of your Gen2 dashboard. (Gen3s have a different preferred display.) This will put you in the most efficient gliding condition. It is not automatically present because drivers just coming from non-hybrids find it a bit disconcerting and out-of-control, coasting too well.
     
  7. srellim234

    srellim234 Senior Member

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    Please get the codes read. You might be scared of what you might see but you might be pleasantly surprised to find an easy solution too. If it does happen to be something major, wouldn't you rather know when the car is sitting in the garage instead of having something go seriously wrong on the interstate, in traffic and miles away from help?
     
  8. Jordan.luna

    Jordan.luna New Member

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    I’m at O’Reillys now so I guess we’ll see
     
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  9. Jordan.luna

    Jordan.luna New Member

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    So I got them read. The only codes were related to the seat position and then another one P0852 which from what I understand isn’t too serious of an issue? I doubt it explains the red triangle. I wish I could at least find out what caused it.
     
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  10. pasadena_commut

    pasadena_commut Active Member

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    Your inverter pump might be on the way out. If the inverter gets hot enough it will set the red triangle. Also my MPG improved each time that pump was replaced (like 42ish to 47ish), even though there was only the one red triangle, briefly, for each of the two pump failures. My best guess is that when the inverter is running hot, but not quite hot enough to set the triangle, it does not work as efficiently. The code for the inverter pump does not set until the inverter gets really hot. I drove for a week back and forth to work with a dead pump (7.5 miles on city streets each way) and it never lit the triangle. When was yours last replaced? The things do not last forever. I might have just hit a bad unit, but the Dorman replacement unit I tried only lasted a month before causing problems. It worked most of the time - but the car overheated when it didn't feel like doing its job.
     
  11. Jordan.luna

    Jordan.luna New Member

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    It might’ve never been replaced. I guess I’ll see if the light comes back on. It hasn’t yet. But now I’m dealing with the effects of letting an overconfident backyard mechanic touch my brakes. I learned my lesson at least.
     
  12. bisco

    bisco cookie crumbler

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    what kind of code does a seat set off?
     
  13. Jordan.luna

    Jordan.luna New Member

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    I honestly didn’t write them down. Something about the seat position and passenger seat position. And some sort of seatbelt sensor.
     
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  14. The Electric Me

    The Electric Me Go Speed Go!

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    But the truth is 11 year old Prius, and you really can't tell. And if you have a symptom like this......

    Then I would say, that's a sign the battery may be failing. BUT....

    I can hope I'm entirely wrong.
    Good news is I often am....
     
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  15. Jordan.luna

    Jordan.luna New Member

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    I have since had the car inspected at a hybrid repair shop and everything is good shape from what they can see. Hopefully it’ll last a little while longer. I’m already saving up for when it needs to be replaced.
     
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  16. bisco

    bisco cookie crumbler

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    there is no connection between the heat and the hybrid battery
     
  17. The Electric Me

    The Electric Me Go Speed Go!

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    Don't necessarily mean to panic you about the battery. And it doesn't sound like you are panicked.
    It's just IMO once a Prius reaches 10+ years the Hybrid Battery simply becomes a potential issue, at any time. But some owners have gone significantly beyond that time frame.
    If you wish to try to extend and parlay this working relationship with the Prius? Then I think it wise to start that Hybrid Battery fund. Then of course hope that you don't need to use it for a while.

    Good Luck.

    Not directly..heat. BUT...
    Doesn't the hybrid battery basically power almost everything electric? Wouldn't that include cabin fan motors?
     
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  18. bisco

    bisco cookie crumbler

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    the cabin fan would be powered by the hybrid battery through the 12v.

    it is a very minimal draw on the system, and is easily tested with the temp set to 'low'

    otoh, the water pump is belt driven, and i'm not sure what happens with the engine off. maybe electrically driven?
    but i think a pulley off the engine, in which case there would be no circulation for the amount of time the engine is off. not sure if that makes sense either
     
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