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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    Our 2011 Prius has ~50,000 miles on it. We live in Nashville, TN (moderately hilly). The main driving we do is a 6 mile round trip each day in the afternoon with stop signs, city traffic, a few hills, 15-20 minutes each way. Temperature depends on the season but mostly about 40 in the winter to 80 in the summer, not too cold because it's afternoon. My wife is the main driver of this car and she says she drives "like a granny". I believe it. We are not carrying anything around, and the tires are fairly new.

    We get about 37 mpg according to the car.

    Does this seem low? Thanks for any input.
     
  2. bisco

    bisco cookie crumbler

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    the 6 mile trip is your biggest problem, prius is best for a lot of driving. how many miles a year have you put on her?
    that being said, there could be something wrong.
    how long have you owned her?
    how many miles on her?
    has the mpg always been low, or has it fallen?
    has all the regular maintenance been done?
    how old is the 12v?
    do you check oil level and tire pressures regularly?

    there are many parts/systems that can affect mpg.
     
  3. Pluggo

    Pluggo Active Member

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    First, forget the car’s self-reported mpg. The only number that matters is when you tank up and divide actual miles by actual gallons. That said, different grannies drive differently. Coasting up to a stop and early braking will make a big difference, as will the handling of hill-climbs and descents, particularly if the hills are somewhat steep and you begin climbing from a dead stop. The hybrid feature does its most valuable fuel-saving work while you’re sitting in traffic, creeping along in a jam or waiting at a light. Other than that, it’s pretty much another compact car. With extra practice and attention and some extra air in the tires I think you might eke out an extra 5 mpg without too much trouble.
     
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  4. Threej

    Threej Member

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    20 minutes to go 3 miles? Personally, I'd switch to a bike.

    But to answer your question, that's totally reasonable mpg. The Prius goes through a warmup cycle that burns a lot of gas on startup, and takes about 5 - 10 miles, temperature and speed depending, to complete. Only afterwards does your MPG start going up.

    If you're finishing your trip before the warmup completes, and you're not doing any fancy MPG tricks, you can expect MPGs in the 30s.
     
  5. jerrymildred

    jerrymildred Senior Member

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    Your profile says Tucson. (It's easy to change that when you move). Based on your membership date, profile location, and present location, I'll fill in the blanks and deduce that you recently moved from Tucson to Nashville and your driving scenario has changed radically.

    Your mileage is not far from what I would expect for a six mile commute in a Prius. It's probably still way better that most other cars in that commute, but not what you're used to. The problem is that, while it's warming up it's borrowing from the traction battery. Once it gets warm enough, the engine works a little harder to repay the loan and get the battery back to its normal state of charge. All that takes somewhere around five minutes. So, by the time it's ready to show what a Prius can do, you're almost to work.

    What you need is a PiP or a Prime. Then you'd get infinite miles per gallon commuting and still be able to take long road trips.

    Oops! I just saw that it's six miles round trip. That's even worse!! Definitely need a bicycle or EV/PHEV.
     
    #5 jerrymildred, Mar 24, 2019
    Last edited: Mar 24, 2019
  6. FuelMiser

    FuelMiser Active Member

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    So you drive 3 miles and shut it down. That is not enough to get the oil warm or blow the contaminants out the tailpipe, let alone charge the 12V and keep the traction battery in the middle. I believe this is considered "harsh duty" in the maintenance schedule due to lots of short trips. You ought to look for an EV in your situation.
     
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  7. ngagun

    ngagun Junior Member

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    Thanks for your reply. To answer your questions:
    - we have owned it since new, 8 years
    - 50,000 miles
    - 6,000 miles/year
    - I believe the mpg has fallen. It's a bit hard to tell because 3 years ago we moved and our driving conditions changed. But I thought the mileage had fallen even before we moved, and I feel like it's fallen more since then too.
    - all regular maintenance has been done
    - the 12v is about 5 years old but I got a gauge for it and it seems to be holding its charge properly
    - yes, we check oil and tire pressure
     
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  8. ngagun

    ngagun Junior Member

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    Thanks for your reply. There is a lot of sitting and traffic and creeping along on our admittedly brief commute.
     
  9. ngagun

    ngagun Junior Member

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    Thanks for your reply. I used to ride a bike to work before I had kids, but now there are two kids to be transferred. So a bike is not an option!
     
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  10. ngagun

    ngagun Junior Member

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    You're right, I updated my profile, thanks for the tip. I think our mileage was decreasing even when we lived in Tucson, and it's been further decreasing since we moved to Nashville three years ago. Definitely the driving situation differs in the two cities, and I'm sure it's a factor, but my gut tells me it doesn't explain all our mileage loss.

    Bike is not an option because there are kids being transported. We aren't looking to get a new car, because given the length of our commute it is almost irrelevant whether we get 37 mpg or 47 mpg, in terms of cost. But I would like to be getting the most out of the car and if there is something wrong with it, I'd like to get it fixed. Thanks again!
     
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  11. ngagun

    ngagun Junior Member

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    Thanks for your reply. Well it's like 3 miles to a daycare facility, 5-10 minutes stopped to pick up the kids, then 3 miles back. Both directions in lots of traffic with some moderate hills. I do understand it's not an optimal commute for mpg!
     
  12. bisco

    bisco cookie crumbler

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    reset a trip meter and take a long drive under varied conditions. this will give you a better idea of mpg performance.
    i suspect 37 is normal for your type of driving, and you'll get close to 50 on a test.

    not much can go wrong at 50k that affects mpg if you're air filter is clean and nothing funky has happened to the car.
    oem tires or replacements?
     
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  13. ngagun

    ngagun Junior Member

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    Can I ask the question another way... Would you expect any difference in mileage for an 8-year old Prius with 50,000 miles compared to when it's new? My guess is we get about 8 mpg worse. It's hard to tell because driving conditions have changed. But I think I pay enough attention to say it's about 8 mpg worse, give or take a bit.
     
  14. ngagun

    ngagun Junior Member

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    The tires were replaced at ~30,000 miles. Tucson roads were very hard on the tires. The current tires are Michelin tires from Costco, I don't know exactly what model, but nothing too crazy.
     
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  15. bisco

    bisco cookie crumbler

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    no, not a noticeable difference. but it is possible you have a weak module, or other unusual issue.
     
  16. bisco

    bisco cookie crumbler

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    if they are not 'low rolling resistance', that can be a factor.
     
  17. audiodave

    audiodave Active Member

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  18. ngagun

    ngagun Junior Member

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    Would a weak module show up on diagnostics when serviced at the dealer? Because we have had most of our service done at the dealer, or a non-dealer Toyota specialist. I've mentioned the low mpg on several occasions but no-one has ever identified any possible cause.
     
  19. ngagun

    ngagun Junior Member

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    I think I got about 40 mpg driving Tucson to Nashville. But I was probably going at 75 mph most of the way... Does that seem reasonable?
     
  20. bisco

    bisco cookie crumbler

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    no, a specific test would have to be done with toyota tech stream diagnostic software, which most dealers don't understand.
    but even a weak module that hasn't gone outside operating parameters yet (you would have a trouble light) shouldn't affect mpg much.
     
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