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Getting great gas millage now i cant get above 45 computer

Discussion in 'Gen 3 Prius Fuel Economy' started by ilovemymac, Jul 11, 2013.

  1. ilovemymac

    ilovemymac Member

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    2010 Prius
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    Have you read This Thead Yet?
    YEs i have

    - What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations)
    IN the 2 months i have had my 2010 Prius V i was getting anywhere from 55-58 computer. My hand caluc show about 3 better on the first several fill ups
    Now im getting 35-40 and no matter how hard i try i cant seem to get it up above that

    - What fuel economy are you expecting and why?
    I was expecting better because i was getting better and not sure what happened

    - What are the approximate outside air temps?
    It has been 80s and 90s. I say 80s and 90s because the temp has been back and forth on each tank. We have had nice days and then days in the mid 90s so id say low 90s average
    - How long are your trips?
    They vary from 15 miles to longer. We go the same places all the time gym, walmart and such.
    How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? (Method Here)
    I have no idea i assume its part of the original car as i cant find that anyone replaced it in the toyota repair logs. I have not checked it because i dont know how on a 2010

    Have you had your alignment checked? Any pulling or abnormal tire wear?
    I had it allined about 1 month ago
    - 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?
    yes stop and go and its cmbo city highway because when i work i deliver so its just me in the car and its all city
    - What's the terrain like of your drives? (e.g. flat, gentle hills, steep hills, etc.)
    Flat and gentle hills nothing steep around here.
    - What are your tire pressures?
    i have 50lbs in each. i have had it that way since i got the car
    - Is your oil overfilled? (i.e. above the full mark on the dipstick)
    no
    - 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.)

    - What region/state are you in? (if you haven't set your location)
    gardner, ks
    - How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking?
    im trying to stay in electric in fact people on the highway i think get mad becuase its 70mpg speed limit and im driving 55 up the hill and then 60+ down.
    - What modes are you using, if any? "normal", EV, power, eco?
    Try to always use Eco mode because i read it makes the AC run more effient
    - Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on?
    no i typically get in and go but i have done that since i got the car

    - Are you driving using D or B mode?
    not sure what that is
    - HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to?
    AC and i dont use auto i try to keep it 78 or 79 with fan on medium or 1 notch above. Except when cooling down the car i turn it on high for a minute or 2 if the car has been sitting all day.

    - 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).
    215//45/17 khumono
    - 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?

    Nothing has changed that i can think of. I am about due for an oil change but other then that i cant see. I have talked to a few on here about putting 205 50 on here for better gas milleage but at the time i was doing pretty good so didnt see the need.
     
  2. kensiko

    kensiko Member

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    test the 12V battery with a voltmeter or a garage battery tester , the battery is at the back of the car in the trunk
     
  3. ilovemymac

    ilovemymac Member

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    Exactly what do I do to test the battery?
     
  4. retired4999

    retired4999 Prius driver since 2005

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    When you get your oil change done ask them to check your battery quick, they maybe will do it for free.
     
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  5. JimN

    JimN Let the games begin!

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    Are you dragging the parking brake? Engage & disengage the brake just to be sure. Ask them to check to see if the wheels spin freely while the car's on the lift.

    If you have the NAV or AT package you can put the map display in Maintenance Mode to get the voltage figures.

    The 12v battery is in the right rear wheel well. Remove the mat, rear deck floor, storage tray, and right side cover (a roughly triangular shaped piece). Everything just fits in place with tabs. You'll see the spare bolted to the car, the rear of the traction battery below the seats and the 12v to the right. As mentioned, use a volt meter to measure the voltage.

    In the photo the empty space to the right of the Optima battery is where you will find the OEM battery. Just based on the age I believe you are due for a new battery but there is no substitute for knowing. I would also get a BatteryMinder to keep the new one charged up. Driving 20000 miles a year isn't enough to keep the battery charged and desulfated.

    You'll need metric sockets (8mm & 10mm?) and will need to get that red contraption off the positive terminal and installed on the new battery. It's a 2 hour job as a worst case.

    A 20mpg drop is unusual. Between winter & summer I'd expect 4 or 5. Just to put your numbers in perspective I got 22.1mpg (indicated) autocrossing in May.

    The only change I recommend is setting the climate control to auto, temp to 78F and outside air flow. I find the car will get cold enough fast enough on this setting. When you get in the car do you drop the windows and turn the fan on low? After a short distance raise the windows & set the CC as above. Now the accumulated hot air is gone so the AC will work faster.
     

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  6. ilovemymac

    ilovemymac Member

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    Will check brake. I never use it.
    As far as the ac I use recercylate I always was told it makes the ac work less because it just uses the cold air inside the Canin vs cooling 90 or 100 degree air from outside.
    I don't use auto I thought that was bad. Yea I typically roll up the windows and leave a little letting hot air out without being all the way open and after a couple minutes I turn ac up and windows up.

    How do I get the nav into main fence mode? In on a 2010 I thought that was only older?
     
  7. ilovemymac

    ilovemymac Member

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    What are we talking price wise for the battery in this? Both 12v and traction.
    My neighbor was saying the big battery will cost 4-5k to replace. That seems excessive.
     
  8. Drdiesel

    Drdiesel Active Member

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    How often do you check your tire pressure. Higher temps will reduce MPG's too.
     
  9. ilovemymac

    ilovemymac Member

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    I check them every few days
     
  10. Drdiesel

    Drdiesel Active Member

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    You should only need to check em every month. Have you checked the oil level ? It's a common problem if you
    don't change your own oil.
     
  11. ilovemymac

    ilovemymac Member

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    I have not recently. I am about due for oil change. And plan on putting in amsoil 0w20. But even that would not cause such a huge drop.
     
  12. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Perhaps you might consider doing a series of mph vs MPG benchmarks:
    • find a flat, no stop, road, say US 56 to the west of town
    • identify a 10 mile segment you can drive on cruise control
    • early in the morning when there is no wind and lowest possible temperatures
    • use cruise control to reach a set speed and reset a trip meter
    • at end, record the MPG and mph
    • turn around and repeat at the same speed
      • average the two to take out elevation and wind effects
    • repeat the test a 10 mph increments
    • record the temperature and weather conditions
    This gives a performance graph:
    1. Compare to what others see
    2. Benchmark the effects of making changes
    Diagnosing a mileage problem is not trivial but a methodical, engineering approach can lead to resolution. It won't be terribly fast, just the only way I know that works.

    BTW, one thing that can help is having a Prius-aware OBD scanner and laptop to record the data. Alternatively, a ScanGaugeII can provide visual metrics that could be video recorded. A recording GPS like a Garmin nuvi could also help. These are tools that can make getting accurate metrics is a lot easier.

    Bob Wilson
     
  13. Drdiesel

    Drdiesel Active Member

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    Oil over filling most certainly can and will cause MPG drop
     
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  14. MPGnutcase

    MPGnutcase Active Member

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    Sometimes it's as simple as a new air filter and tire pressure, when I had my brother-in-laws car over we pulled the air filter [he's a guy you would never want to buy his used car] the air filter looked like I dipped it in dirty motor oil then buried it in the garden. Wish I took a picture of it............
     
  15. fuzzy1

    fuzzy1 Senior Member

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    Excessive use of electric mode has hurt the of mpg of many neophyte drivers. While electric has its place at low speed, don't force it at highway speed, nor use it for acceleration above about 15-20 mph. Glide with engine off when you can, but the great bulk of propulsion should come from the gasoline engine, not the electric motors and battery.
    This is the 'gear' shift selection (P, R, N, D, B). Forward motion should almost always use 'D'. Save 'B' for downhills long and steep enough to put the brakes at risk of overheating, something you are unlikely to encounter in your area. Incorrect use of 'B' won't hurt the car, but will cut MPG.

    A dirty air filter has far less impact on MPG in traditional cars (Otto cycle engines) than most people are led to believe. The restricted airflow just substitutes for some of the throttle butterfly valve action, which is never fully opened in ordinary driving. It has to be dirty enough to sharply cut power and hamper driveability before the MPG starts falling. But your b-i-l's case may have surpassed that threshold.

    But low tire pressure is a very common MPG killer.
     
  16. ilovemymac

    ilovemymac Member

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    I use D mode then. I know B is only for like mountains and stuff.
    I can check the air filter i havent looked at it yet
    I run 50LBS in the tires or 49. Thats more then i see anyone here running. But again i have not changed that since we bought the car

    I got into the maintenance mode but all i get is the 3 things it checks all say OK. SO i dont know where i can find voltage that everyone talks about seeing.
     
  17. fuzzy1

    fuzzy1 Senior Member

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    The voltage readout is for GenII only. The GenIII requires you to bring your own voltmeter.
     
  18. ilovemymac

    ilovemymac Member

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    OK what am i looking for and how to i check with a voltage meter?
    Sorry if i ask to many questions. But thank you all for all the help you provide it means allot
     
  19. ilovemymac

    ilovemymac Member

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    Did a 10 mile stretch up and down 56 hwy here like you said. Got 45mpg at the end. I will do it again tomorrow morning.
    I drove for work tonight stop and go around town got 45mpg as well driving 50 miles I think.
     
  20. Drdiesel

    Drdiesel Active Member

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    Have you checked the oil level ?