Bad MPG (25mpg) - New 12V battery - How do I test the Hybrid Battery with diagnostic?

Discussion in 'Gen 2 Prius Fuel Economy' started by Adam M, Mar 3, 2016.

  1. Adam M

    Adam M New Member

    Joined:
    Mar 3, 2016
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    Location:
    Western Pennsylvania
    Vehicle:
    2008 Prius
    Model:
    Two
    Help. How can I know if Hybrid Battery is causing Poor Gas Mileage? I have a 2008 Prius with 130k miles and average 25 mpg in winter and 32 mpg in summer. Other Prius owners in my area are getting 40 and 50 mpg respectively. Thanks in advance!

    - Have you read This Thead Yet? file:///C:/Users/Adam/Downloads/Why_Don't_I_Get_The_EPA_Mileage.pdf
    yes
    - What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations)
    manual calculations, 26mpg average over past year
    - What fuel economy are you expecting and why?
    expecting at least 40mpg because it's a hybrid Prius
    - What are the approximate outside air temps?
    outside ranges from 20F in winter to 90F in hottest of summer.
    - How long are your trips?
    on average my trips are 5 to 10 miles (15 to 20 minutes)
    How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? (Method Here)
    Replaced the 12v battery with brand new about 3 months ago hoping this would fix the mpg issue
    Have you had your alignment checked? Any pulling or abnormal tire wear?
    Yes. Alignment is good. No pulling or abnormal tire wear.
    - How much of it is city vs. highway? Roughly what's the average speed in overall and and of each segment? Is there a lot of stop and go driving?
    Mostly City driving, average speed is 40mph
    - What's the terrain like of your drives? (e.g. flat, gentle hills, steep hills, etc.)
    Combination. I live in flat but there are gentle and steep hills in any given trip.
    - What are your tire pressures?
    Tire pressures are set to recommended as per inside of driver's side door. (34 to 36 psi (?)
    - Is your oil overfilled? (i.e. above the full mark on the dipstick)
    Oil is less than full mark
    - Make, model, year, engine and transmission of previous car? (e.g. 08 Honda Civic Si 2.0L 4 cylinder, manual transmission) What did you actually get on the same trips/commute? (Please give us actual numbers, not EPA ratings.)
    Previous car(s) were 02' Subaru Forrester and I got 30-32mpg consistantly. Same with '06 Honda CRV
    - What region/state are you in? (if you haven't set your location)
    Western PA
    - How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking?
    trying to stay in electric only
    - What modes are you using, if any? "normal", EV, power, eco?
    not sure of this. If there is a default in the 2008 Prius, that is what I am in.
    - Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on?
    Sometimes, but not usually
    - Are you driving using D or B mode?
    D
    - HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to?
    Heater is set between 68 to 75 in winter depending on climate, but NOT using Auto mode and I frequently will run it on medium to low or no.
    - Are you using the factory tires and wheels? If not, please indicate tire make, model and size (e.g. Goodyear Assurance Fuel Max 185/65R15).
    Not using Factory tires but same rims. It is cold and night now so I can report this later if anyone is interested.
    - If reporting a mileage drop, did anything significant change on your car (e.g. accident, hit a curb or big pothole throwing off alignment, oil change/other maintenance/repairs, changed tires or wheels, etc.) or your commute?
    Not reporting a mileage drop, this poor mpg performance has been an issue since I purchased the vehicle in August of 2014. Average only 25 mpg in winter and 32 mpg in summer.

    2014-09-06_12-03-51_491.jpg
     

    Attached Files:

  2. wjtracy

    wjtracy Senior Member

    Joined:
    Sep 19, 2006
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    Location:
    Northern VA (NoVA)
    Vehicle:
    2006 Prius
    Western PA ah yes my home territory. Well with the hills you're hoping for 40-45 MPG. The only time we see MPG that bad is short trips of course the system never warms up. What I like to do is get out on a level road doing 50-55 MPH after warm up (10-15 mins) you should be seeing bars hitting 50 MPG.

    Need to check tire type, alignment, also we see sometimes the brakes are too tight grabbing and you will notice the wheels do not spin freely when jacked up you should be able to spin wheel freely. Of course Hybrid battery issue but normally you'd know that. Then maybe some deposits in the air/fuel flow need cleaning I am not the expert there but that's one other thing.

    Spark plugs should be replaced by 120k miles but honestly I did not do it until 132k. If plugs have been replaced hope the correct type was used and occasionally one may be loose or something on a DIY replacement job.
     
    #2 wjtracy, Mar 3, 2016
    Last edited: Mar 4, 2016
    uart likes this.
  3. dolj

    dolj Senior Member

    Joined:
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    Location:
    Wellington, New Zealand
    Vehicle:
    2006 Prius
    The only three things that stand out to me are your short trips, the OAT in winter and your tire pressures.

    The first two you can't really do anything about. Try running your tires at 39 PSI front and 37 PSI rear.

    If you do the run at 50-55 mph (pick one) as suggested by wjtracy and use the cruise control (if you have it), and you can get around 50 mpg, then you do not have any real problem. Just a combination of how you use the car.

    Let us know how it goes.
     
    uart likes this.
  4. Eastside

    Eastside Member

    Joined:
    Feb 24, 2016
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    Location:
    NorthVirginia
    Vehicle:
    2005 Prius
    MPG up significantly today. The 2005 Prius feels like a 40+ mpg sports car again.

    I replaced the air filter after six months use. The new one has Made in Japan molded in the rubber gasket. Old one didn't
    Old and new both from Toyota dealers. Old one surprisingly dirty. Good work filter, and ugh, that's the air we are breathing.

    I think our gas is now a Summer blend. and I also topped off tire pressure a little.
     
  5. wjtracy

    wjtracy Senior Member

    Joined:
    Sep 19, 2006
    10,506
    3,112
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    Location:
    Northern VA (NoVA)
    Vehicle:
    2006 Prius
    ..mine too but it's old and I'm replacing lots of parts to keep it running
     
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