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05 MPG down to 35...what's wrong?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Ken S, Jul 24, 2010.

  1. richard schumacher

    richard schumacher shortbus driver

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    How often do you check the tires? What are they now?
    Do you ever check the oil level yourself? What is it now?
     
  2. Ken S

    Ken S Member

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    I can check those, but wheel alignment feels good...I'm not seeing any uneven wear on the tires or pull on the wheel.
     
  3. snead_c

    snead_c Jam Ma's Car

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    Engine air filter ?
    Poor gas ? Increased % ethanol ? :confused:
     
  4. 2009Prius

    2009Prius A Wimpy DIYer

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    If the parking brake is not dragging then I wonder if the OP drives in the EV mode too excessively to the point that the health of the HV battery is damaged.

    There was a national lab study showing no MPG impact by very dirty air filter on modern cars with computer controlled ICEs.
     
  5. Ken S

    Ken S Member

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    I check them every time I fill up which is roughly every three weeks.
    Oil level I check right after it's changed. I also checked it a couple of times recently to see if there was a problem. It has stayed steady right at the full mark.






    iPad ?
     
  6. Ken S

    Ken S Member

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    I don't have an EV mode switch and frankly don't try to do hyper-mpg type of driving. Whether I get 43 mpg or 46mpg isn't that important to me. This mileage drop is of concern because it's indicative of a problem.

    I just wonder if the water pump that went bad had a negative effect on the health of the main battery. Are there any on board diags. that check the health of the system?

    Someone asked about fuel. When I noticed the problem I started using different gas stations. I know they change the amount of ethanol in gas seasonally, but I've never seen this dramatic a drop before.





    iPad ?
     
  7. 2009Prius

    2009Prius A Wimpy DIYer

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    By "EV mode" I meant
    . If one drives with yellow arrow only from battery to wheels for a long period of time then the HV battery may be stressed.

    By the way how is Tapatalk working for you?
     
  8. Ken S

    Ken S Member

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    Well, a large part of my drive is in the 35 - 45 MPH speed range...but I never tried to do that.

    I'm wondering if there's something with the A/C not operating efficiently that could be putting a greater load on the car. The car gets cool...I generally keep the thermostat set on Auto at 76, but with the hot summer we've been having it has to work.

    Tapatalk is alright and is certainly better than using Safari to peruse forums....typing on the iPad is painful. :)
     
  9. GasSaver1

    GasSaver1 Member

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    I am in south florida too and I am getting about 35mpg too....
    Two weekends ago I took a drive up to orlando and got 47mpg- last weekend I was stuck in very slow moving traffic on 95 and got close to 60mpg.

    I dont think there is anything wrong with my prius or yours for that matter- south florida sucks nice person when it comes to the roads. At least in the ft lauderdale area, you get slammed with lights everywhere and can never really cruise enough to get proper gas mileage. Not to mention that it has been so hot (close to 100).

    The slow moving stop and go like in bumper to bumper traffic is great because the battery does all the work, but ive noticed that the lights down here are not timed in any sense of the word so often you have to accelerate from a stop, make it roughly 200ft and are stopping again. Unless you do one of those reaaalllly sloooow egg shell on the gas move, this will kill the gas mileage.
     
  10. 2009Prius

    2009Prius A Wimpy DIYer

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    Hmmm.... at 35 - 45 MPH one would expect 60+ MPG unless it's all short trips or stop and go traffic.

    There are cases of A/C failures but I haven't heard of cases of inefficient A/C causing MPG drop but then again anything is possible I suppose.

    Have you checked the parking brake drag? That would be an easy one to fix.

    I can say typing on an iPhone is even worse. ;)
     
  11. 2009Prius

    2009Prius A Wimpy DIYer

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    1 person likes this.
  12. snead_c

    snead_c Jam Ma's Car

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  13. richard schumacher

    richard schumacher shortbus driver

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    Thanks for the updates. So now we turn to the weather: MPGs on mine have also dropped during the last three weeks of 100'F+ temperatures. The heat inhibits the battery system, so stop-and-go fuel economy suffers even more than usual, and of course it makes the A/C work harder. At night when it's merely 90'F or so outside and the highways are clear the MPGs go right back up.

    Does any of that fit your circumstances? If so then the cure is called "October" :_>
     
    1 person likes this.
  14. Ken S

    Ken S Member

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    Thought I'd report back.

    1. Installed a new battery
    2. I've run several tanks of gas from different stations since then.
    3. Daytime temps here in South Florida have been steady at 90 for months now. That's not much different from previous years.
    4. Tire Pressure roughly 38 psi

    Two Toyota dealers and a 3rd party mechanic who I really trust tell me there are no negative diagnostic codes.

    Overall MPG has been 35.
    Highway MPG (Avg 65 MPH) 37

    A year ago and for the previous 4 years:
    Overall MPG: 44
    Highway MPG 39
     
  15. cwerdna

    cwerdna Senior Member

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    What are the make, model and size of tires you have now?

    Do you remember what you had before? Where they the stock Goodyear Integrities that came on non-tourings?
     
  16. 2009Prius

    2009Prius A Wimpy DIYer

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    Has parking brake drag been ruled out yet?

    How about a weak HV battery?
     
  17. ursle

    ursle Gas miser

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    If the oil were 2/3rd's up to the full mark it would yield optimum mileage.
    I'm thinking something funny is going on with your cooling system, check to see if the trans axle recirculating pump is working properly. Human mechanical mistakes are not out of the realm of imagination.
    Clean your cabin air filter.
    Cycle your emergency brake on and off a few times.
    Change your trans axle fluid.
    Did you put an optima or original equipment battery in?
    (An OEM battery isn't going to last, it's money down the drain.)
    Do a fresh reset of your mileage total, if it's getting better mileage now a low average would take a long time to overcome.
    Change your engine air filter(clean it if it's a K&N filter).
    One misfiring spark plug would yield this type of mileage but should show up as an error when reading the OBD11, but stranger things have happened.
    jmho,ymmv
     
  18. andyprius

    andyprius Senior Member

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    Unfortunate and typical dealer reaction. This problem has been a recurring one since 2001. Congradulations on the dead battery right at the dealership, I did the same thing in 2005.
     
  19. Bob64

    Bob64 Sapphire of the Blue Sky

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    Have you checked your engine/cabin air filters? If your running the A/C, perhaps a clogged cabin filter is reducing the A/C efficiency.

    And finally :has your commute changed? Shorter trips?
     
  20. Ken S

    Ken S Member

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    I've never had the stock tires...when I bought the car the dealer had installed (mandatory) 17-inch wheels. I don't have the exact tire sizing right now...but they're 17s and made by Toyo. I had Michelins before that. The Toyos have been far quieter (less road noise) than the Michelins were.

    I've had the Toyos for quite a bit longer than I've had the fuel problem.