Our mileage is disappointing, wondering if it's normal

Discussion in 'Gen 3 Prius Fuel Economy' started by ngagun, Mar 23, 2019.

  1. ngagun

    ngagun Junior Member

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    The tires are Michelin Defender XT. Does anyone know if they would have an effect on mpg?
     
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  2. bisco

    bisco cookie crumbler

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    yes, up to 5 mpg negative
     
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  3. bisco

    bisco cookie crumbler

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    great tire though, many happy reports here
     
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  4. FuelMiser

    FuelMiser Active Member

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    You might want to check the tires for their economy rating. Prius does best with low rolling resistance (LRR) tires. Most brands put an ECO or Green type label on the sidewall, even a leaf. Tirerack.com can give you the specs on your particular model. Poor tires will definitely give lower MPG results. And you said you noticed this even before moving to Nashville...
     
  5. ngagun

    ngagun Junior Member

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    I think it probably is the tires. (I actually don't think the tires are that great in other respects either, honestly--the car easily slides on hills in the rain, and handling feels sloppy in general.)

    But I think our fuel economy is not as bad as I thought. I drove the car 18 miles yesterday over 6 or 7 trips, and got 53.5 mpg. It was mostly fairly optimal driving conditions (30-50 mph, good weather, not too many hills). Makes me think I am probably only 2 or 3 mpg down on what the mileage was when new, and that can probably be attributed to the tires.
     
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  6. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    Michelin Defender XT are maybe a Costco iteration? Some have the "Green-X" label, and the latest version has been saying "Total Performance". I'm not sure that they've change much, are a good tire, decent rolling resistance.

    Regarding the recent drop in mpg, try a fuel injector cleaner, the kind you pour into the tank at fuel-up. Look for a good rated one with PolyEtherAmine (PEA), which is supposedly quite effective at cleaning the injectors.

    Your 12 volt battery may be undercharged, with the short trips. If practical with your parking situation, consider getting a smart charger, 3~4 amp range, one that can be left on indefinitely, if needed. Plug it in on days when the car will not be used, and leave it hooked up until next drive.

    Exhaust Gas Recirculation circuit may be starting to clog. I kinda hate to mention it, but it's pretty much inevitable, with all 3rd gens. Not sure how much it might impact fuel economy though.

    For short trips:

    1. Consider getting the Toyota block heater installed. That'll raise the coolant temp around 20~30C. Temp plateaus around that level with about 2 hours plugged in. Plan for the time you forget to unplug, ensure the cord is very secure at the car, and the extension cord is also secure, and will pull out easily.

    2. "Severe service" was mentioned up the page. Repeated short trips is one criteria constituting severe service. Consider doubling up the service interval, to 6 months or 5K miles, whichever comes first. FWIW, just across the 49th parallel, Toyota Canada calls that the regular oil change interval, for 3rd gen. (With 4th gen they're in line with the US.)

    Tips:

    1. Especially when partially warmed, experiment with turning the cabin temp down, and/or the AC off (if it's running). Or turning the vent system right off, rolling windows down instead. The car will shut down a partially warmed engine at red lights much more readily, if there's little or no cabin heat/vent demands.

    2. Consolidate trips as much as possible. Avoid "impulse" trips, especially short ones, or consider walking if practical.

    BTW: our situation is similar, if not worse, lol. We're now putting around 6000~7000 kms a year on the car, lol.
     
  7. ngagun

    ngagun Junior Member

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    Thanks for all of these tips. I will give some of these things a try for sure. I am especially suspicious of the 12v battery.
     
  8. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    Check it's voltage with a digital meter, first thing in the morning, preferably with the hood left ajar the night before. Just opening the car doors to pop the hood (assuming you check at the jump point, in the under-the-hood fuse box), will drop the measured voltage somewhat.

    upload_2019-3-25_7-19-8.png

    If you get a reading 12.6 or higher, say up to 12.9, the battery should be in pretty good shape.

    For a more complete assessment, most battery retailers will test the battery with an electronic load tester, for free. Dealerships will also do it, but might charge $50~75 for the service, and aren't that convenient.

    You can DIY the test with something like Solar BA5. The connection with these testers has to be right at the battery, directly to the posts.
     
  9. amos

    amos Active Member

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    I drive on a weekly base l.a to vegas avg speed of 75 mph with one stop. My tires are worn and are never the best condition no LRR. I average 50 mpg.
    I noticed when driving in vegas it goes to 56mpg. Driving in l.a i get 42 mpg.
    Hope that helps
     
  10. audiodave

    audiodave Active Member

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  11. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    Funny, I put a like on that without even checking what thread I was in, because it's never a bad idea, lol.
     
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  12. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    I drive 60 MPH where it is VERY flat. (it gains 90 feet in 156 miles) so my mileage is just a reflection of how warm the car is. (and which way the wind is blowing)

    In Winter, the mileage may level out in 20 miles, in Summer under 10 miles. never under 3 miles. beyond that I get fabulous mileage.

    [​IMG]
     
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  13. karl.d

    karl.d Junior Member

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    What is the ethanol content of the gas that you regularly use ?

    You can try an A/B test by comparing mileage based on gas with minimal or no ethanol content compared to the regular gas that you buy .

    Do not put a higher octane gas in Prius as it will surely complain (Atkinson cycle issues with higher octane).

    In 2014, toyota made changes to the prius engine for efficiency. Toyota introducing new series of gasoline engines with gain of at least 10% fuel efficiency; up to 38% maximum thermal efficiency - Green Car Congress
    So in comparing notes with others, may be helpful to see if they have the same engine as your model year.

    IMO (rather an uneducated suspicion), 2011 Prius engine was engineered for a time when our gas did not have increasing percentage of ethanol. A few years ago, there used to be lines stretching out the local Safeway for people to gas up because of favorable price. Today, not much of a line anymore at local Safeway even though their pricing is still favorable. Somebody knows something I don't.
     
  14. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    They may have been developing new engines in 2014, I don't see this meaning the 2014 Prius model year engine was any different. Having said that, 2014 saw a revised piston, and 2015 revised piston rings, but those two changes were in effort to stem oil consumption issues.
     
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  15. ASRDogman

    ASRDogman Active Member

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    My 2002 Town&Country is a flex fuel motor, as were other vehicles. I think Toyota knew about the ethanol in the fuel.
    It's about the rubber and gasket seals they use, the ethanol will eat the older seals. And I guess some software info
    for the computers.
     
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