07 Prius really bad mpg

Discussion in 'Gen 2 Prius Fuel Economy' started by Cibelly Aguiar, Nov 2, 2018.

  1. Cibelly Aguiar

    Cibelly Aguiar Junior Member

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    Hello everyone,

    I have been posting in this forum for awhile and you guys are really helpful. I am trying to figure out whatever can be happening to my car; I've been reading a lot about it, but I don't really understand the lingo used in most part of the posts. I've read many posts here from people that had poor mpg, but I didn't relate to them. For that reason, I am opening a new thread here, but I don't mean to sound repetitive.

    So, I have a Prius with 178k miles. I got it about a year ago with 174k miles. I've been doing maintenance, changed the tires to winter tires (I live in Boston-MA), changed oil recently, try not delay any maintenance care (even though the mechanics I take the car to always say that there's nothing to worry about). I've been getting 24mpg lately. I calculate when I refuel the car by zeroing the ODO and the averages. I've been doing 200 miles or less with a full tank which is around 7 gallons here.

    When I start calculating, the monitor shows me 38mpg, and then it drops to 27mpg and less sometimes. And it doesn't feel accurate to what I do with the car. Is there something I should worry about? I am taking the car to a company called "Prius Kings" to have the HV battery tested over the weekend. Also, I do a lot of short trips (5 minute trip to work). I heard that these short trips can kill mpg, is there something to do so it doesn't affect as much the mpg? When I got the car, last year it would do at least 45mpg. I would refuel the car once a month, now it's been 4 days and I only have 3 blips left with less than 100 miles traveled.

    The picture I uploaded is the photo of how the battery is most of the time when I get home and when I live the house, and then the mpg I've been getting with 105 miles traveled.

    Thank you for your help!
     

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  2. SFO

    SFO Senior Member

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  3. JC91006

    JC91006 Senior Member

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    Don't waste your money with the battery test, your bad mpg is due to your 5 minute drive. The prius only gets efficient after it completes it's warm up stages. You are already at your destination by the time that happens.

    Also the use of the heater/ac will reduce the mpg too
     
  4. jerrymildred

    jerrymildred Senior Member

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    What JC said.

    Also, unless you live at the bottom of a big hill, I wouldn't expect the battery to be in the green when you get home. Probably in the upper blue area. I gather that you're in a lot of stop and go traffic. That will drive up the battery charge and, with your short trips, you never get the chance to use it up.

    Short trips are the bane of fuel economy for any car. The advice I hear most often is to combine your trips. But at only 4,000 miles a year, perhaps you don't have very many trips to combine.
     
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  5. srellim234

    srellim234 Senior Member

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    If you are not already doing so, you might get a little help by allowing the gas engine to cycle through one time before you drive away. It automatically comes on a few seconds after you power it up. The car is much more efficient after that engine turns off at the start of your drive.

    Now that you're into the colder seasons the car's mileage tends to drop anyway. Gas engine warm-up times increase. Also, using the defroster and heater will cause the gas engine to fire up more often.

    The main culprit, as expressed above, is the short time of your drives. The car is designed to be driven and it's not even getting time to warm up before you're turning it off again. During times of the year when I have to use my car like yours I will drop from the normal 43 mpg to 34 mpg in decent weather with no a/c, heater or defroster use.
     
  6. bisco

    bisco cookie crumbler

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    Winter tires can be an mpg killer, check the pressures

    How are you calculating mpgs

    A block heater might help, try to do as many errands in one trip as possible

    Drive to the furthest, and work your way home

    Prius kings is a chain, be careful, and don’t let them talk you into anything
     
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  7. sam spade 2

    sam spade 2 Senior Member

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    AND.....you can't really trust the onboard computed MPG numbers.
    Reset the ODO and divide miles driven by gallons put in the tank.......over several fills.

    But it sounds like you have enough different indications that you know the mileage isn't really that good.

    Alas, with a 5 minute trip to work and back it might not get any better.

    Have you considered a bicycle ? City bus ?
    Plug-in hybrid ??
     
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  8. SFO

    SFO Senior Member

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    Don't forget partial blocking of the radiator during the winter months.
     
  9. bisco

    bisco cookie crumbler

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    4,000 miles per year is more than 10 miles per day.

    The surprising thing is that you were getting 45 mpg when you first bought it.
     
  10. bisco

    bisco cookie crumbler

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    Some things not yet mentioned that can bring down mpgs on an older car:

    12 v

    Hybrid battery

    Fuel injectors

    Plugs and coils

    Oil burning

    Air and cabin filters

    Throttle body and maf
     
  11. 05PreeUs

    05PreeUs Senior Member

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    As there is no mention of any warning lights, we can presume there is nothing the ECM can "see" that is causing the higher than expected fuel consumption. This suggests that the AFR (air fuel ratio) is correct and that the engine is operating normally, be aware that it is more than possible to have a bad sparkplug or coil and no fault codes or warning lights; either of those will drive up fuel burn.

    As we have started seeing colder weather, it is important to remember two important things about a Prius:
    1) If you make high heating demands, the engine RUNS to warm up the coolant
    2) If the coolant is too cold, the aux heater is activated to make up the difference

    If BOTH are happening, that burns a TON of fuel because the engine is running to warm up the coolant AND providing HV power to the grid (aux) heater circuits. Why would this be? Well it seems like the coolant is either not staying warm (thermos system is malfunctioning) or the thermostat is, causing colder than normal engine operation; which BTW will, all by itself, increases fuel burn.
     
  12. Al Bundy

    Al Bundy Member

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    has anyone mentioned the bladder in the gas tank dosent expand as easily in cold weather so you are getting less fuel in the car when you fill it up..
     
  13. 05PreeUs

    05PreeUs Senior Member

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    No. Based on what? Even if so, the OP clearly understands that MPG = Miles driven / gallons burned as they stated that only 7 gallons was used to go ~ 200 miles.
     
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  14. opticell

    opticell Junior Member

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    If I had to drive 5 minutes twice daily, which I've done when I live couple miles from work, MPG will suffer, but you should be able to boost to 37-40 MPG.

    For these 5 minute short trips, when outside temps are below 50F,
    - 100% grill blocking. I use Coroplast free from the local carpet store. (They are the backing to carpet sample foldouts and are discarded often) This helps for warm up, and also for maintaining ICE temps when engine may be running but not under much load.
    - Keep heater off
    - watch instant MPG indicator, to keep above 50 as much as possible.
    - no warm up,
    - get to speed and let off accelerator just enough to maintain speed.

    Pull grill blocking for longer trips, unless you can monitor ICE coolant temp.
    ps. I've been using grill blocking during winters in Utah for 9 years now. I get 50mpg in summers, and drop to 44mpg as outside temps reach 32F (without grill blocking). With blocking, my mpg returns to 50mpg even in cold winter days. Started this with my 2004 Prius blocking all but the bottom, and my 2010 Prius blocking 100% of bottom grill. I keep designing 12v auto Louvers in my head, but have yet to make one. I should say your winter mpg with blocking won't improve more than what you normally get in summer mpg without it. How you drive will get you to 50mpg ?can? be easy, even 60mpg is possible but harder.
     
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  15. bisco

    bisco cookie crumbler

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    great tips, thank you!(y)
     
  16. Cibelly Aguiar

    Cibelly Aguiar Junior Member

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    Thank you for the tips! I will look up some videos on how to do the grill blocking on mine. I think that I need to start "driving" better the Prius, because almost never MPG indicator is above 50. And when someone else drives the car, like my sister, I notice that she can keep it up above 50 without even caring it lol.

    When you say "no warm up" you mean like not letting the car running to heat it up? Because when it is really cold here, I usually go to the car, turn it on and turn the heat up so it is warmer when I have to leave, than I turn down the heat to low.
     
  17. bisco

    bisco cookie crumbler

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    what did prius kings have to say?
     
  18. Cibelly Aguiar

    Cibelly Aguiar Junior Member

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    They said that the battery was fine. Doing what it’s expected. The 12v is also good. The technician gave me some tips on understanding the MPG monitor, and now I am learning to drive it “better”. But it’s winter, so not very good results because I’ve been using the heater.
     
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  19. Christina.cmb

    Christina.cmb Junior Member

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    Whats this mean?
     
  20. jerrymildred

    jerrymildred Senior Member

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    There are countless threads about it here. This is one:
    grill blocking | PriusChat

    Not something you'll be having any need for unless maybe you're going to Tahoe in the winder.
     
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