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Could this be accurate?

Discussion in 'Gen 3 Prius Fuel Economy' started by s1njin, Jan 3, 2011.

  1. s1njin

    s1njin New Member

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    I posted pieces of this in the main thread as a 'welcome aboard' type thing, but I thought I'd get a more concentrated opinion by posting the conolidated effort here:

    *******************************
    The background:
    I am running my stock OEM Goodyear tires at 38/36 to start off. I figure it will be a happy medium from whats on the placard and the pressures they hyper milers are running. I want to see how this works out for me. I actually put in 40/38, but the garage was 50 degrees - when things settle back into the 30s here in PA my pressures should be close to what I'm gunning for.

    Taking it for its first run to work tomorrow AM. 36 miles one way, back roads, some hills, and a final 8 mile run down a highway with a few stop lights. Any car I've ever driven gave me mileage very close to the highway estimate than the city - I'm hoping my mileage comes in as expected once my car breaks in.

    *********
    The result of my first trip:

    I have no idea if this is accurate or not, but I just completed my first trip to work. I reset my trip 'a' and the const read out on the hybrid drive display reads 61.5. I was careful about staying in the Eco zone, backing off the gas and coming back easy to use the battery, etc. Gas gauge still reads full !

    It's 28 degrees out here but the car started outing my garage.

    *******

    Could this be right?

    Thanks gang,

    s1njin
     
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Due to various factors, a lifetime pump gallons used/ Odometer miles is the MOST accurate, but it is fun to show co-workers numbers like yours!
     
  3. F8L

    F8L Protecting Habitat & AG Lands

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    Did you reset the trip and MPG gauge before allowing the car to warm up or after the car was warm? If you reset your MPG gauge after the car was warmed up or after you have started driving then you will not achieve an accurate measurement.

    Make the same trip back home to get a more accurate estimate of your MPG after the change in tire pressure. A commute route can return excellent MPG one way but not so great on the return trip. This is the case with almost all of my routes. Also not temperature and wind differences between your morning and evening commute.

    As an example, my commute to my girlfriend's house is 37miles of freeway driving (Rocklin, CA to Davis CA). The route appears flat but going to her house I can achieve 58-60mph (speed is kept between 65-70mpg). On the return trip, my MPG is reduced to 48-50mpg.
     
  4. s1njin

    s1njin New Member

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    I reset the trip meter in the garage before I backed out for my first run. :)
     
  5. F8L

    F8L Protecting Habitat & AG Lands

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    Perfect! Now run the same trip back home and report back to us. :D
     
  6. s1njin

    s1njin New Member

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    I would expect it to be somewhat worse as the general layout of the ride has me going a bit more uphill. Should be in the same ballpark though.

    Even if that estimate is 10% off, I'm happy as all hell w/ it !
     
  7. F8L

    F8L Protecting Habitat & AG Lands

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    I would be too!

    I drove from Davis to Sebastopol yesterday (170+miles). Temps in the 40-50s and through much rain with 4 passengers and I still achieved a round trip mpg of 47.6. I feel that is pretty damn good considering we stopped for a long lunch and my average freeway speed was 70-75mph.
     
  8. Mendel Leisk

    Mendel Leisk Senior Member

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    Nice numbers!

    If that's your typical driving it should work good for you. Like any car, it is the really short trips that are most detrimental. Once warmed up the Prius is actually more economical in town than highway, due it it's strong battery.

    I just buckled down and started a spreadsheet for our consumption, we've had 2~3 half tank fill ups to date. I found the in-dash mileage display to be 7.5% optimistic, which is an irritant: who do they think they're kidding?

    Anyway, in a mix of around town and highway, some short, some long, over Christmas we got (calculated) 5.2 liters/100km, translates to 45.3 mpg.

    That's on Michelin XIce in the base model size on steel rims. Was super wet a week or two back, and now clear and cold, temps around zero Centrigrade.
     
  9. F8L

    F8L Protecting Habitat & AG Lands

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    Mendel, please keep the spreadsheet updated for at least 10 tank refills and report back in the sticky thread regarding MPG calculated vs. displayed. We know that the GenII Prius was approx. 2%-3% optimistic. I would love to see the numbers for the GenIII as many of us feel that the numbers are even more optimistic for the GenIII.
     
  10. tumbleweed

    tumbleweed Senior Member

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    Most of us who kept fairly careful records and checked the mileage over several thousand miles found the Gen 3 consumption read out to be optimistic by about 4% to 5%.
     
  11. s1njin

    s1njin New Member

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    Well heck, if the CONST reading I got for my trip read 61.5, even at 5% off its still around 58.5 mpg. I'm assuming the CONST reading is the reading over the life of my trip reset?

    I'm stoked !
     
  12. Mendel Leisk

    Mendel Leisk Senior Member

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    Could be the way I'm calculating the percent:

    calc'd minus in-dash, divided by calc'd, times 100

    FWIW: in-dash was 4.8 and calc'd was 5.2 (liters per 100 km). This is the first calc I've got serious, started a spreadsheet, but the last couple of half tanks were similar I think: roughly a 0.3~0.4 error.

    I'll do a few more tanks then post to the sticky thread. FYI, Honda's the other way 'round: calc'd is usually better ;)
     
  13. tumbleweed

    tumbleweed Senior Member

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    You should be, that's pretty good.
     
  14. s1njin

    s1njin New Member

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    Okay, so going home for the first time (differant route due to traffic issues), I got 54.1 MPG. I expected it to be less because:

    A. The car was in the parking lot all day (hence 37 degrees cold)
    B. Going home is uphill, going to work is downhill

    All in all? I'm pretty satisfied. Beyond belief. What a great car, I probably spent MAYBE 1.5 gallons of gas on a trip that would have cost me 3.4 in the other car. That's real money folks.
     
  15. s1njin

    s1njin New Member

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    I assume it IS accurate. I took the same route to work this AM as I did yesterday - 60.8 mpg. I figured it would be less as I hit more stop lights than I did the day prior.

    No jack rabbit starts and I spent prescious little time in the 'power' band of the display.

    Real glad I picked up this car !
     
  16. s1njin

    s1njin New Member

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    My first fillup nets me 54.14 mpg. I didn't top off the tank - I just let it go till it popped.

    So it would seem the CONST values I was seeing are somewhat optimistic.
     
  17. Tideland Prius

    Tideland Prius Moderator of the North
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    Like you wouldn't imagine. I was stoked that I was keeping L/100km figures below 5.0L/100km (48mpg) even with -20C temps but calculated netted me 5.2L/100km (about 46mpg) . I'm still impressed but that's a rather large discrepancy (my best tank of 4.1L/100km or 58mpg turned out to be closer to 4.3 or 4.4L/100km or about 54mpg)
     
  18. F8L

    F8L Protecting Habitat & AG Lands

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    That is not good. I wish they would have designed a more accurate system. Your MPG in such conditions is pretty impressive. I wouldn't expect anything less from you. ;)
     
  19. Tideland Prius

    Tideland Prius Moderator of the North
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    Makes me sad given that the '05 was fairly accurate. This makes it hard for me to get the 3.7L/100km official city rating. It probably means I need at least 3.5L/100km showing on the MFD.

    I still can't match Evan or Tony's mpg.
     
  20. Troyroy

    Troyroy Member

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    I'm envious of all of you. I have trouble getting more then 40 MPG..about the time I get into the 41 or 42 MPG area......a hill comes up.....then it's back into the 40 if I'm lucky. With the snow & ice.....I guess that I'm running the heater & rear window deicer too much. Yes......I do have the lower grill 100% blocked.

    Still the best mile per gallon that I have ever gotten........love the Prius !!!!