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2005 with 140k getting 25-29mpg

Discussion in 'Gen 2 Prius Fuel Economy' started by HDuncan, Jun 11, 2014.

  1. HDuncan

    HDuncan Member

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    - Have you read This Thead Yet?
    Yes. I don't feel my mileage should be this bad, unless it is a serious accumulation of issues.


    - What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations)
    trip computer. See attached screen shot


    - What fuel economy are you expecting and why?
    I've hit 70mpg in this car before using pulse and glide. My girlfriend drives the car, and while she doesn't know the pulse and glide method, 29 mpg seems abysmal for a prius. I can get my VW GTI to do better!

    - What are the approximate outside air temps?
    about 95-100 right now.

    - How long are your trips?
    Average trip is about 3-4 miles one way.

    - 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?
    All city. Not much stop and go.

    - What region/state are you in? (if you haven't set your location in your profile)
    Central California

    - What's the terrain like of your drives? (e.g. flat, gentle hills, steep hills, etc.)
    mostly flat, but some very subtle grades.

    - Is your oil overfilled? (i.e. above the full mark on the dipstick)
    Oil seems right at the top of the second bump on the dip stick, but doesn't appear to be "over".

    How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? (Method Here)
    Checked it - seems good. Though, it did show as being .1 too low in part 1 of the test procedure. I just replaced the battery about 6 months ago, so I think it is probably okay.

    Have you had your alignment checked? Any pulling or abnormal tire wear?
    Alignment hasn't been checked. No noticeable pulling.

    - 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).
    Am using the following:
    Sumic GT65A
    185/65/R15

    - What are your tire pressures?
    Front Driver = 43
    Back Driver = 38.5
    Front Passenger = 43
    Back Passenger = 44

    Not sure why the back Driver was lower, but promptly set it to 44.


    - 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.)
    I drove the Prius for about 7 years. Girlfriend's first car.

    - How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking?
    She brakes somewhat hard, doesn't try to stay in electric - she just "drives".

    - Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on?
    No. Jump in and go.

    - Are you driving using D or B mode?
    D mode.

    - HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to?
    For a while, no AC and terrible mpg, recently, AC has been on manual mode set to about 75 and fan about medium speed. It was 104F today.

    - 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 to report.

    Mileage was terrible - then I realized that my coolant pump had gone out, and the serp belt was shredded from the wobbly pully. I replaced the belt and the pump myself, expecting that would help with the MPG and it doesn't seem to have made much difference. The car hasn't beens serviced since about 115k. I am considering replacing the spark plugs next. Just waiting to hear back from the Dealer to see when the plugs were last replaced according to their records (if its only been 50k I don't think it would make sense to change them out.)
     

    Attached Files:

    #1 HDuncan, Jun 11, 2014
  2. fuzzy1

    fuzzy1 Senior Member

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    These are the items that jump out at me. High outside temperatures make the AC work hard, though you also mention previous no-AC problems.

    Short trips carry a significant penalty for engine warm-up, in both hybrids and traditional cars, because the warm-up fuel gets averaged out over just a few miles.

    City traffic with numerous stops carries some cost, and waiting time for traffic lights boosts the apparent cost of AC. But city speeds themselves are ideal when done with little or no stopping.

    Hard braking defeats the regenerative braking by sending most of the potential energy into the brake pads instead of the battery.

    But I'm no so sure these are enough to account for the low mpg. Can you test with a longer trip at highway speed? Ideal would be to reset the MPG readout after warming up the engine. This is easy with GenIII models and their trip gauges, but is different on 2005 model. For GenIIs, you might need to warm the engine, then go fill up the gas tank to reset that display.
     
    #2 fuzzy1, Jun 11, 2014
    Last edited: Jun 11, 2014
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  3. HDuncan

    HDuncan Member

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    In the attached photo, couldn't I just hit the reset button after warming up for 5 minutes? I don't understand what filling up does to the trip meter.
     
    #3 HDuncan, Jun 11, 2014
  4. fuzzy1

    fuzzy1 Senior Member

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    If your MPG display works on the trip meter that way, instead of being reset only by refilling the tank, then yes. I don't have a GenII, just know that its MPG displays work different than my newer vintage.

    BTW, for other testing, I meant to say highway speed, not high speed.
     
    #4 fuzzy1, Jun 11, 2014
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  5. HDuncan

    HDuncan Member

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    Hmm I guess I've always assumed that the MPGs only refer to the miles driven after hitting reset.

    When I hit reset, the MPG goes to zero, which makes me feel that the reset button resets both the total miles as well as the MPG.

    Could be wrong but I'll try it anyway and report back!
     
    #5 HDuncan, Jun 11, 2014
  6. HDuncan

    HDuncan Member

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    [QUOTE="fuzzy1, post: 202[/QUOTE]BTW, for other testing, I meant to say highway speed, not high speed.[/QUOTE]

    >;)
     
    #6 HDuncan, Jun 11, 2014
  7. tanglefoot

    tanglefoot Whee!

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    I think the short length of trip is the largest factor. If the trip doesn't take much longer than 5 minutes, 25 mpg is pretty typical for the first 5 minutes of driving. It takes about 10 minutes of driving for the 5-min segment to get into the 40s or so. After about 15 minutes of driving, the system is usually in its later warm-up stages, for optimal mpg. The best averages are possible with trips of at least 30 minutes each way.

    I learned (from the forum) that the behavior of the mpg average reset is different in the early 2nd gen and late 2nd gen. On earlier cars, the mpg average resets at fuel fill-up. On later cars (I believe 2006-2009), the mpg average does not reset at fuel fill-up. On all cars, the "reset" button should reset both the mpg average and mile counter on the MFD.
     
    #7 tanglefoot, Jun 11, 2014
    Last edited: Jun 11, 2014
  8. uart

    uart Senior Member

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    Does anyone know anything about these tires? Google seems to indicate Sumic are basically the same a Doral tires. No firm data on the specific model number, but I'm pretty sure that others here before have complained of an MPG hit with Doral tires.
     
    #8 uart, Jun 11, 2014
  9. fuzzy1

    fuzzy1 Senior Member

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    I may be confusing this with the automatic tank MPG feature on GenIIs, or maybe just some of them as suggested by Tanglefoot. GenIII models lack this automatic measurement, annoying numerous former GenII owners.
     
    #9 fuzzy1, Jun 11, 2014
  10. bisco

    bisco cookie crumbler

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    any idea when the mpg's dropped, and what were they before? was it a sudden drop, or a steady decline?
     
    #10 bisco, Jun 11, 2014
  11. nh7o

    nh7o Off grid since 1980

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    Try a straight and level test somewhere, after the car is totally warmed up, so that the engine shuts down when coasting and stopping. Hold a speed of ~35mph and see what the instantaneous MPG says. The car should easily make close to 50mpg.
     
    #11 nh7o, Jun 12, 2014
  12. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. How long was the car driven with a failed engine coolant pump?

    2. Do you believe that the poor mpg started at around the same time that the coolant pump failed?

    If your answer to #2 is yes, then I would say that it is likely the engine sustained permanent damage from being overheated, causing the poor fuel economy to continue. The Prius engine construction is all-aluminum and the engine will not tolerate any significant overheating. To verify that engine damage is present, you would need to have an engine compression or cylinder leakdown test done.

    3. I agree with the suggestion that you should take the car for a long drive on level terrain at ~40 mph which will give you an idea of the best fuel economy that the car can achieve.
     
    #12 Patrick Wong, Jun 13, 2014
  13. Jamesb93612

    Jamesb93612 Member

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    Hey HDuncan. I have an '08 and I live in Fresno. I have seen my MPG drop from 45 to about 39. I am attributing it to the extreme heat we have been having and the fact that the A/C is working hard. The odd thing is that I have had my car for 3 years and do not remember having such bad mileage. Hope you figure it out. It can be frustrating to have a car that was purchased for the high MPG and not be able to achieve it.
     
    #13 Jamesb93612, Jun 13, 2014
  14. Patrick Wong

    Patrick Wong DIY Enthusiast

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    In that case, make the Prius READY, turn on the AC to MAX COLD, open the hood and look at the sight glass in the air conditioner refrigerant line to see if any bubbling is present. If so, that shows you there is a slight refrigerant leak which results in the AC compressor running more than otherwise necessary. That would cause a decline in fuel economy.
     
    #14 Patrick Wong, Jun 13, 2014
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  15. Jamesb93612

    Jamesb93612 Member

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    Thanks! I'll have to check that out.
     
    #15 Jamesb93612, Jun 13, 2014
  16. fuzzy1

    fuzzy1 Senior Member

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    Should a check for coolant pump failure be added to Cwerdna's questionnaire?
     
    #16 fuzzy1, Jun 13, 2014
  17. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Well, that is a specific example of the general concept of a powertrain failure. Certainly, such a failure will have an adverse impact on fuel economy.

    In this case, the failure was most likely avoidable, it requires the vehicle owner to inspect the engine once in a while for coolant seepage below the coolant pump. This can be done at the same time that the engine oil level and all other engine compartment fluid levels are checked, while refueling for example.

    If the water pump bearing was actually wobbling so the serpentine belt was damaged, I would expect one or both of the following to accompany that problem: 1) substantial coolant leakage, and 2) unusual noise caused by the failing pump bearing. Either issue could be noticed by the alert owner.

    Regarding the questionnaire, if the owner does not notice a powertrain issue, it is unlikely s/he will provide an accurate answer to a question on that topic. So it is not obvious that the questionnaire would benefit from the addition of that question.
     
    #17 Patrick Wong, Jun 13, 2014
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  18. HDuncan

    HDuncan Member

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    Hey Everyone - sorry for the hiatus. I did take the car out on two highway trips (about 30 minute drive at 50-65mph) and got it up to 44mpg. Does this seem reasonable or should I be expecting better?


    I'll do my best to answer the questions:

    Bisco: I think it was a slow and steady decline... I think I would have noticed. But I wasn't the main driver so it might have been sudden. my girlfriend did all of a sudden start complaining about the mileage, so maybe it was more sudden.

    Nh70: I'll give that a shot tonight

    Patrick:
    1. How long was the car driven with a failed engine coolant pump?
    I think it may have been several weeks. We did notice a sound like a diesel engine. I looked on the forum for answers and heard people saying that sometimes the prius sounds kind of diesely, so I assumed it was fine. I took it on a long trip and that's when it got really bad, and a month later, BOOm the serp belt was trashed and I noticed the water pump pulley was wobbly.

    2. Do you believe that the poor mpg started at around the same time that the coolant pump failed?
    I have no idea, but it is certainly possible.

    If your answer to #2 is yes, then I would say that it is likely the engine sustained permanent damage from being overheated, causing the poor fuel economy to continue. The Prius engine construction is all-aluminum and the engine will not tolerate any significant overheating. To verify that engine damage is present, you would need to have an engine compression or cylinder leakdown test done.
    I'll put this in my notes for the next time the car is in the shop. Thanks for the idea!

    3. I agree with the suggestion that you should take the car for a long drive on level terrain at ~40 mph which will give you an idea of the best fuel economy that the car can achieve.
    I will do this tonight and report back.


    Jamesb93612 - thanks for the condolences =) Maybe it is just the heat. I am hoping its nothing serious but I'll definitely try to pay back the forum by sharing what I find.



    As far as adding this to the list of mpg questions. I think Patrick is right. Though, I was alert, I did notice the noise, but I didn't find anything on the message board that made me worry. If I had seen anyone talk about a water pump failure, and known about the potential MAJOR overheating concern, I would have definitely checked it out before I started getting the temp warning alert messages.
     
    #18 HDuncan, Jun 16, 2014
  19. Patrick Wong

    Patrick Wong DIY Enthusiast

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    That isn't bad considering you have to utilize California-formula gasoline. If the car is getting on average only 25-29 mpg then the next step is to analyze the typical driving usage and determine why this results in such poor fuel economy. For example one of your answers indicated the car is only driven 3-4 miles at a time. In that case the engine doesn't have a chance to warm up sufficiently to reach "normal" fuel economy levels.
     
    #19 Patrick Wong, Jun 16, 2014
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