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MPG trials with different parameters

Discussion in 'Gen III 2010+ Prius Fuel Economy' started by NineScorpions, Jan 17, 2012.

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  1. NineScorpions

    NineScorpions Economy, Meet Style!!

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    When buying the Pri, I learned all the techniques. However I have tried to enter each parameter one by one to measure the impact. My only mistake (if you want to call it that) was not getting a couple of tanks under my belt with the stock wheels / tires. The great news is that the weather is quite stable...so these should be relative apples and apples with some percentage of slop. I started with:

    No ECO mode
    No tire pressure adjustments (31 PSI original)
    No lowering spings installed
    Aftermarket wheels and tires installed
    Average temperature: 65
    Fuel: Shell; all tanks same gas station; even same pump
    Same driving techniques over each tank
    *Initial tank of gas was excluded...was learning how to drive the damn car.

    My first full tank trial was with the 18" rims and tires only (no ECO, no pressure adjustments, no springs).
    Result: 43.2MPG actual (46.0 computer)

    Second tank...I added the 1" lowering springs only...still no ECO and no pressure increase in tires.
    Result: 43.4MPG actual (46.6 computer)

    Third tank...I now have rims/tires, lowering springs, and have now engaged ECO mode only. Still no tire pressure changes.
    Results: 45.3MPG actual (48.4 computer)

    Fourth tank...rims and tires, lowering springs, ECO engaged, and now tire pressures increased from 31 PSI to 42 front and 40 rear.
    Results: 46.2MPG (49.2 computer)

    With my setup with all changes...I am estimating to see 46MPG, perhaps 47MPG with the same weather conditions. As the weather warms...I assume I can see potentially hit 49 or even 50MPG mark. This would be sweet with the big and heavy shoes I put on the car. I will update this in the coming weeks with my findings. I guess the last trial will be to slap on the stock wheels and tires and see how depressed I become :eek:

    Anyone else have trials similar and what were your results?

    **Updated 29-Jan in red
  2. Insight-I Owner

    Insight-I Owner 2006 Insight-I MT + 2011 Prius

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    Nice scientific approach. Yes it would be good to go back to stock for a baseline.

    I probably would have done something methodical like you did but I was happy with the results right off. I just aired up the tires to 44psi and the first full tank was 61.8mpg actual (65mpg on the display) and the next 7 summer tanks were even higher (several at 65mpg actual). Then colder weather and winter RFG hit and I'm struggling in the high 50's. Somewhere in there I took off the ugly plastic wheel covers and added a Scangauge, but that's it.

    I probably drive slower than you do, which is a big factor. 15" wheels and higher tire pressures probably help, and those higher numbers are from the summer. I can't figure out how to pulse and glide, so I don't. Around town I stick to the speed limits and try to run electric as much as I can, especially if no one is behind me. I try to be aware of traffic behind me, but if someone wants to go 45 in a 25 I'm not going to go 45 just to keep them happy!
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  3. F8L

    F8L Protecting Habitat & AG Lands

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    Nine, please complete your testing then go back to the 15" wheels with high pressure and let us know how it goes. This will help rule out the driving skill variable. As you put down more miles you learn how to drive the car more efficiently. I never used to be able to get 50mpg for the first year I owned the car but later I was able to eclipse 50mpg on a regular basis with no other changes.

    Depending on your average speed I bet you could get 50mpg in the summer even with your 18's. It may take some practice. Also keep in mind that gliding is much easier with LRR 15" tires so hypermiling techniques can increase your max mpg difference between the 15s and 18s. If you never try to glide or coast the. The mpg difference between the 2 tires sizes is smaller.
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  4. NineScorpions

    NineScorpions Economy, Meet Style!!

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    Insight, those are some great numbers you are hitting :) I tend to drive just a tick over the speed limit in town and 65-70 on the interstate. I am very interested to see how much of an impact warmer weather will actually bring.

    F8L, I will update this when I finish the current and next tank. You are right...even though I probably do not think it...you get betterr with time and I hear the car itself tends to natural increase mileage after the first few thousand miles.
  5. quickdrawgc

    quickdrawgc New Member

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    I just finished the first tank in my 2011 II with all base features. It looks like I got about 48.75 mpg (calculated, not the display). My morning mileage is much worse than afternoon, I'm in florida but its still in the 40's and 50's in the morning and I seem to use a lot more gas when the engine is cold (car doesn't fit in garage yet). I'm in the 2nd tank now and I'm tracking the mileage a little closer and more of the miles are on the highway. Looks like I'm getting (on the display) about 47/48 mpg, so probably 4-5 less than that if my car holds to what a lot of folks are saying (up to 5 miles off the display for real mileage).

    I'm interested in seeing what happens if I up the pressure in the tires (I'm at whatever the dealer had them at).

    Since you guys seem to know a lot about the wheels / tires, do you use nitrogen in the tires? The dealer wanted to charge me like $100 for it, but I can get it put in for free next time I visit the dealer my family works for. Have you noticed much of a gain from it?
  6. Insight-I Owner

    Insight-I Owner 2006 Insight-I MT + 2011 Prius

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    My HSD usually reads about 5% high, so that would be 2.5mpg at 50mpg.


    You'll probably see a few mpg improvement. What you'll also get: longer tire life, quicker steering, braking probably about the same. If you drive sporty you may or may not notice less grip, and you may or may not notice a bumpier ride.
    Probably wise to raise the pressure a few mpg at a time and see how you like it, rather than go up a lot all at once.


    I never bother. Air is 78% nitrogen, so all you're doing is removing (if they flush and refill several times) the other gases. I try to use dry air, which means air from a pump or compressor at home rather than one at a gas station.
  7. ksstathead

    ksstathead Active Member

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    I also use the 78% nitrogen blend. :)
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  8. kgall

    kgall Active Member

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    LOL.
    I'm 60 and that's the first time I've ever seen that phrase used.
    Will the car go on a diet or will the garage grow?
  9. ksstathead

    ksstathead Active Member

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    Perhaps a lower viscosity external lubricant?
  10. quickdrawgc

    quickdrawgc New Member

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    Funny :D

    No the garage needs to lose some weight after the holiday re-org. I've still got the Christmas decoration boxes and the remains of all of the "why the hell is this in the garage?" stuff after I put up the new garage shelves all sitting in the middle of the floor.
  11. kgall

    kgall Active Member

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    Nine, what was your "unadjusted" tire pressure? You may be pleasantly surprised when you go back to stock wheels and near maximum rated tire pressure.

    Where in Texas are you?
    Here in central Ark., I find that the two biggest things that change my gas milage are temperature and wind. Maybe wind even more than temperature.
    You are being more scientific about it than I've been.
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  12. NineScorpions

    NineScorpions Economy, Meet Style!!

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    Thanks! I have not been scientific enough...because I did not record PSI at the intervals. I will check them tomorrow and start tracking. And I agree with you...temperature and wind make the biggest impact. In the cooler morning hours to work...my mileage struggles. But in the evening warmer hours...it is much easier to hold or increase my average. I am in South Texas...just north of Mexico and very close to South Padre Island.

    And my garage is big enough for my Pri...but only because it replaced a big V8...so it fits quite nicely :D Almost done with the current tank!
  13. SuperchargedMR2

    SuperchargedMR2 Diehard Rams Fan

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    One other thought too, have you checked how accurate your odometer is with a GPS unit? I checked my 07 Corolla last week & while the speedometer is almost perfect, the odometer was recording 4% fewer miles then my Garmin GPS. I'm not sure what is going on with this but it was just a thought.

    Has anyone else done this too? And BTW, my Prius fits in my garage too! :lol:
  14. NineScorpions

    NineScorpions Economy, Meet Style!!

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    just updated my original post with new results.
  15. NineScorpions

    NineScorpions Economy, Meet Style!!

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    31 PSI (set by Discount Tire). I have not touch them since the install back in Dec.
  16. NineScorpions

    NineScorpions Economy, Meet Style!!

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    I will check during this week. All of my data is calculated. I am seeing the car caluclating about 3MPG above the actual calculated. I will add this to my original post.
  17. SuperchargedMR2

    SuperchargedMR2 Diehard Rams Fan

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    I've always done calculated numbers too but then I found that my odometer was showing me fewer miles then I was actually going which ended up giving me a lower mpg figure then I was actually traveling, even though it was calculated. :eek:
  18. NineScorpions

    NineScorpions Economy, Meet Style!!

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    ok, now I gotcha. So yours was 4% off? I will have to check mine tomorrow.
  19. kgall

    kgall Active Member

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    Never been down there. The furthest south we've been on the Texas coast is the Aransas Nat'l Wildlife Refuge, where we were lucky enough to see a few of the elusive whooping cranes.


    On the issue of odometers--my odometer seems to be pretty good when used against measured miles on interstates. (This in contrast to some of my previous cars which seemed to register a few percent high--an extra tenth or two over five miles)

    I'm surprised at odometers reading low--given the consumer pressure against rolled back or otherwise dishonest odometers.
    I wonder what could be causing it? Tire size, inflation, wear (or lack of it) ???????
  20. SuperchargedMR2

    SuperchargedMR2 Diehard Rams Fan

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    On my 07 Corolla it was. I went 100 miles on my odometer but my GPS showed that I went 104 miles. I haven't checked my Prius yet.
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