Short trip tips?

Discussion in 'Gen 2 Prius Fuel Economy' started by pasadena_commut, May 2, 2019.

  1. pasadena_commut

    pasadena_commut Junior Member

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    Greetings all.

    Recently bought a 2007 Prius to replace a Honda Civic Hybrid which was having an assortment of issues. My drive to work is just 7-7.5 miles each way which usually takes about 25 minutes. So the Prius (and any other car but an EV) spends a large fraction of the trip warming up and running at low efficiency. The Prius has a nice graph which demonstrates that on the MFD display. In the morning that plot is a nearly straight line from the ~23 mpg for the first 5 minutes to ~55 mpg for the last. In the afternoon it does better, warming up to ~50 mpg after "just" 10 minutes. That is probably the result of the combination of a higher ambient temperatures and warmer coolant in the "thermos". (Just a guess until I can run the car with a computer plugged into the OBD2 port.) There is also a gradual elevation change to consider - it about 400' higher at work than at home.

    It is still on the first tank but all display indications are that the car is returning about 39 mpg.

    Are there any tricks which have been reliably shown to improve efficiency with a driving pattern like that? I am open to making some modifications to the car. Seems like a grill block might help it warm up a bit faster. In the AM a block heater run for a while before starting the car might help. It would not fully warm up the car, and would make no difference for the catalytic converters, but it might make the AM trip closer to the mpg of the PM one.

    Sites I have visited were unanimous in asserting that letting the car idle to warm it up was not a useful way to improve mpg because gas burned in that mode returns zero miles. That is of course true, but in theory a vehicle might have an especially efficient warm up mode, where every joule of energy from the gas burned results in maximal temperature increases in the oil, coolant, and especially the catalytic converters. Also because the car would not be moving there would be no losses to friction (other than in the ICE). A moving car will lose more heat to the air passing through it than will a sitting car. So I'm wondering if anybody has run across a test somewhere that actually demonstrated that the dogma is actually true.
     
  2. Mendel Leisk

    Mendel Leisk Obtuse Angler

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    Block heater will help a bit.

    The part's maybe $80 (genuine Toyota). Install is a bear; if a dealership will do it for $200~250 all-in I'd be temped.
     
  3. srellim234

    srellim234 Senior Member

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    I'm thinking the car is either right where it should be or even a little better than that if your screen is accurate. Like the inaccurate gas gauge, on certain cars under certain driving conditions the gas mileage readout can be off as much as 5 mpg either way from tank to tank. While the mileage gauge is normally a little optimistic, when I look at my records I find it calculates the other way about 20% of the time on my car. For example, I just topped off my tank since I'm driving to Phoenix around 2 am and after 274 miles of the last tank the screen was reading 38.7 mpg. The calculated average was 43.5 mpg.

    It has a lot to do with the rubber bladder gas tank and its inconsistencies.It will take a few tanks, calculated out, to really get a feel for what mileage you're actually getting.

    There is a definite learning curve to these cars too. The most efficient driving style is different than a Honda. As I've read here over the last 3 years, the most efficient acceleration is around 2400 rpm, something that can be seen with the Torque Pro or Hybrid Assistant apps and a bluetooth connector under the steering wheel. The plug-in is about $10-15 on Amazon and the apps are anywhere from free to about $7.50 in the Google Play Store. Those apps also read and clear codes, give you a running account of the health of the car, the batteries plus a lot of other information. The Hybrid Assistant even goes as far as helping indicate whether you are hitting the brakes with too much vigor and wasting energy.
     
  4. Usle

    Usle Member

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    Let me speak straight.
    Your traction battery 1600$ to buy another 1000$to install, (use a toyota dealer) is fried, just replace it, then check your 12 volt, then your brakes.
    Toyotas are dependable, just do the upkeep. 39 is not 55, it's 40% less, it will work for you at 39, but for 2600$+- it could work better for you.
     
  5. fuzzy1

    fuzzy1 Senior Member

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    Bicycle. (Too long for good walking shoes.)
    The difference between 39 MPG (current) and 50 MPG (desired?) is costing you less than a half gallon per week. Keep that in mind when choosing how much to spend in trying to improve this.

    And remember that your 2007 Prius is EPA rated for only 48/46/45 MPG, not 50.

    My old rule of thumb, created under a prior non-hybrid and still useful on the Prius, is that a warmup cycle from a cold start costs the equivalent of roughly two miles of fuel on a warmed up engine. That means a 7 mile trip from a cold start will burn about the same fuel as 9 miles on an already warmed engine, which is how EPA ratings are tested. So 50 MPG warm drops to just 50 * (7/9) = 39 MPG cold.

    Prius partially breaks out of this pattern on really short trips where the engine doesn't fully warm up. But your 7 miles & 25 minutes should produce a full warmup, so doesn't fit into this exception.

    Best Solutions to this short-trip warm-up problem?
    (1) Good walking shoes (not practical for 7 miles);
    (2) Bicycle (excellent fit for this distance);
    (3) A true plug-in electric car.
     
  6. bisco

    bisco cookie crumbler

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    my commute was 7 miles each way. i always got 55 in summer and 45 in winter in both my 04 and 08.

    there is likely something(s) wrong with your car
     
  7. fuzzy1

    fuzzy1 Senior Member

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    How much time did it take? This is relevant to comparing how much stop-and-go is involved.
     
  8. bisco

    bisco cookie crumbler

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    about 20 minutes. 4 miles of 30-40 mph, only 3 stops, then 2 miles of highway at 55mph, then 1 mile of 30 mph and 1 stop before arriving.
    return is similar.
     
  9. TMR-JWAP

    TMR-JWAP Senior Member

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    You are right in the ball park of where I would expect that car to be. I base this merely on the drive my son has for his work for about the last year. It's also a relatively short trip, but not nearly as time consuming as yours. He seems to always be in that 38-40 mpg area now. If I use his car for my drive, it's right back to mid-high 40's, exactly as it's always been. Very similar numbers to the blue 2005 he used prior to the current 2005.

    My 2007 has been breaking personal records left and right this spring. My last tank was 55.6mpg with ~ 490 miles when I filled her up just after reaching one dot. That's with a 22 mile/27 minute trip each way, Monday - Friday. Maybe I need one of those Red Bullet vvt solenoids to reach 60+mpg with my unmodified 183k mile clunker...your mpg is going to vary greatly based on driving style, weather and the actual drive.
     
  10. pasadena_commut

    pasadena_commut Junior Member

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    For me usually there are at least 20 stops each way. Top speed is 45 mph but only on a short section, at best .5 mile.
     
  11. bisco

    bisco cookie crumbler

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    that's a lot of stops, and will reduce mpg. it's not actually the stops, it's the starts.
    try a trial run without as many stops, find a 7 mile drive in the country.
     
    #11 bisco, May 3, 2019
    Last edited: May 3, 2019
  12. Prodigyplace

    Prodigyplace Senior Member

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    A yes run as opposed to a no run ? :confused:o_O
     
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  13. srellim234

    srellim234 Senior Member

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    How in the world did you determine from the information given that the hybrid battery is bad? For that matter, how did you determine that anything is actually wrong with the car? Besides, a new hybrid battery is not necessarily going to guarantee much of an improvement in gas mileage. Many are yielding about the same gas mileage they did when new right up until the battery failure.

    Not every Prius is going to yield 50 mpg(US). They only average 43. Those over 50 are an anomaly showing some do give way above average mileage in certain individual Prii under certain conditions. It shouldn't be expected, though, and we should be realistic when attempting to aid new Prius owners.

    When someone is asking how to get a little better mileage, you don't suggest a $3000 replacement he doesn't need. Why didn't you just suggest he spend $32,000+ on a brand new Prius Prime Advanced that will virtually guarantee he'll get well over 50 mpg?

    pasadena_commut has a car that is perfectly normal for the way it is being driven. Short trips and slightly uphill in the morning combined with short trips primarily downhill in the evening are yielding 39 on his screen. That screen can be off by 4 or 5 mpg either way. Better LRR tires or higher tire pressure might help. A block heater should help. More experience learning the nuances of driving his individual Prius instead of his previous Honda will help the most.
     
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  14. Mendel Leisk

    Mendel Leisk Obtuse Angler

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    I was with you except for that bit, lol. To put it politely, Toyota is an incorrigible BS'er with the mpg display; it'll be off by 4 or 5 mpg all right, but always in one direction.
     
  15. srellim234

    srellim234 Senior Member

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    Not so. I find that with the inconsistencies of the fuel bladder it can go the other way about 20% of the time on my car. Some examples noted in my expense log book for this year already:

    Screen 41.8, calculated 37.54
    Screen 42.4, calculated 43.37
    Screen 38.7, calculated 43.46
    Screen 42.7, calculated 37.76
    Screen 44.0, calculated 46.0

    A great example of why, with the fuel bladder and different pumps' shutoff points, it's necessary to judge fuel mileage and what's happening with it by calculating over multiple tanks, not depending on one tank or the MFD screen.
     
  16. Mendel Leisk

    Mendel Leisk Obtuse Angler

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    Yeah, that was the one thing I could see causing under-reporting of mpg: vagaries of the 2nd gen bladder. Still, I'd wager if you averaged the variations, over the long they'd be well to the positive side.

    At least if it's anything like third gen. My average variation is around 7.5%. Helps being able to do relatively consistent fills.

    upload_2019-5-4_8-1-4.png

    (Lower numbers are better.)
    (Last tank, I seem to be getting wacked by new tires. :()
     
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  17. srellim234

    srellim234 Senior Member

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    Correct you are on that point. The fuel mileage is definitely overestimated on the screen overall.
     
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  18. Prodigyplace

    Prodigyplace Senior Member

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    Every Gen 4 & Prime, driven reasonably, should average over 50 MPG. I agree your comment applies to Gen 1 - 3 though.
    The EPA Combined for my Gen 4 is 52 MPG. With over half highway driving I strive for between high 50s & low 60s in the summer..
     
  19. Mendel Leisk

    Mendel Leisk Obtuse Angler

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    Yeah if you look at Fuelly, you can see the jump in mpg with each gen. Big jump with fourth gen... :cautious:
     
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  20. Raytheeagle

    Raytheeagle Senior Member

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    Not to mention the Prime :).
     
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