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found my sweet spot mph on hwy

Discussion in 'Gen 2 Prius Fuel Economy' started by abra, Jun 2, 2008.

  1. abra

    abra Member

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    went for a road trip this week. found out how far off my mpg avg is too.
    set cruise at 68mph (speed limit was 70mph)
    total fill up at 229miles was only 3.6 = 63.61:D

    road info:
    hwy 71 from kansas city to i44 to springfield mo temp around 70 light wind from the west (5mph) light rain too

    trip back with no rain, only 1 pip went off:eek: at 101 miles, found out on mine that the frist pip is 1.4 gallons ( total trip back 136 miles)

    this is off, but a good avg
    [​IMG]
     
  2. Sheepdog

    Sheepdog C'Mere Sheepie!

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    be careful with that last pip nonsense. walking sucks!

    and any speed over 60 is asking for lower mpg. over 60 the resistance from the air itself will defeat you. Try 55 and see the improvement!
     
  3. CalvinL

    CalvinL 2013 Prius Persona Black Cherry Pearl

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    Well it depends I suppose. To me, It doesn't really matter how slow or fast you drive - or even how much mpg you get although they all give a great feeling of environmentalism, conservationism and having something truely innovative. The bottom line is cost to drive over time and not just on a daily basis.
    I keep track of both my actual mileage after a fill-up and the onboard computer computed avg in an old post about my old 2005 model: http://priuschat.com/forums/prius-main-forum/38116-trade-values.html

    I have both the actual and average of the computed/onboard mileage and you can see that there's a 5mpg difference. Currently, in my 2008 model, 2554 miles driven over a total of 60.4 gallons, I'm getting about 42.3mpg actual versus the onboard average of 43.21mpg.

    *heh* I suck!!! But hopefully, I will have many more miles to get this number back up!!!! But as Sheepdog said: "Try 55 and see the improvement!" (although I've achieved 60mpg at urmm... over 65mph too... :p

    Here's an interesting post I've found that references 85mpg and some myths and facts about our cars: Toyota PRIUS: It is not a car but a phenomenon! - by M. Kostic
    He made some note about the high compression versus the octane/regular grade gasoline - but I think with today's electronics, there are probably methods to control this - for example, you ever notice your top speed can vary depending on weather, battery, etc? I think because once the engine power caps out, the rest is upto the battery and electronics which can vary depending on the programming.

    I keep a simple spreadsheet that does most of my culculating for me. It's quite nice when you see the high numbers :) but you also know if you've been naughty when you get under 45mpg :)

    Here are the fields I use:
    Date(of fuel up), TripCounter, Total Mileage, Gallons, Total Cost, Cost per gallon, cost per mile, Octane, miles per gallon, onboard mpg.

    It's on my pda so its a little hard to download at the moment - and I'm lazy. But I fill this thing out religiously at the pump even if people are waiting :p It's kinda fun to know if you've been driving naughty or conservative :p
     
  4. Lord_Towers

    Lord_Towers Noobie :)

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    i was under the impression that basing your MPG off off the amount of fuel your bladder took at a fill up could give some seriously flawed results

    I've read on here that sometimes you just can't get a "full" tank and there may be a gallon or so of room left in the tank.
     
  5. avdavsim

    avdavsim New Member

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    Screw Sammy Hagar, I can drive 55!

    When I was doing the 65-70 "keep up with traffic" thing, I was getting about 46 mpg. I set my mind to going 55 and bearing whatever slings and arrows were cast at me. Of course, I keep scrupulously to the right-most, non-exit-only lane.

    Since then, I have been getting around 55 mpg. This is based on about 6 tanks since I've been doing it, but I have had two anomalous tanks, the past two times. First, I got close to 60 when the consumption indicator said I was averaging about 53, and then I got 41 when the gauge had me at 50. I am assuming that the bladder effect gave me a short tank for the first one, and made up for it in the second.

    It's my weekend driving, going to lots of places that kills my great mileage. If I gas up Monday morning and fill up on Friday evening, I find that my commuting mileage is in the awesome range.
     
  6. JimboK

    JimboK One owner, low mileage

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    That's true for a single fillup. I have tracked the difference between displayed MPG and calculated MPG at each fillup since last October. I've seen as much as a 15% difference in a tank. Calculated MPG will become more accurate as results from more tanks are factored in. Currently the cumulative difference is 2.3%.
     
  7. bruceha_2000

    bruceha_2000 Senior Member

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    Same here and I have data for a LOT more than 6 tanks. I do a 400 mile round trip every Monday. 55 MPH vs 65 MPH nets about a 10 MPG improvement - figure it at about 20% less fuel used/mile.

    I did TWO 400 mile trips in 3 days this past weekend. The first at 65 MPH (had 3 passengers) and managed just under 47 overall. Got gas 190 miles from home (10 cents cheaper) and got home still at about 47. 400 mile round trip by myself on Monday at 55 MPH netted 54 MPG for those miles AND the first 190. Calculated MPG for the 400 miles at 55 MPH is about 58 MPG.
     
  8. 08Prius

    08Prius New Member

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    This image has been scaled down to fit your computer screen. Click on it to show it in the original size.​
    [​IMG]
     
  9. jammin012

    jammin012 The man behind The Man

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    I also keep track but it was the Life Cycle studdy that got me intersted. I did a spread sheet for the Jaguar also to see where I stood when I traded it in.

    So right now my 07 Package 4 + all the money I've put in the car, i.e. accessories, gas, and insurance, with 9950 miles on it, costs me $3.05/mile to drive. Considering the first mile cost me $27,000 I'd say I'm doing pretty good. The more I drive the less it costs.

    The Jag at trade in cost me $0.91/mile and you're looking at 80K at trade in.

    In 4 years the Jag cost me $72,800. I could probably find more cost if I looked harder.
     
  10. jammin012

    jammin012 The man behind The Man

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    08Prius, nice pic. But I get over 60mpg right after a fill up too, mainly because it's in town and the ice IS OFF. Let's see what that reads after 300 or so. If you're still in at 60 them PROPS TO YOU. I'm getting 43.
     
  11. PriusSport

    PriusSport senior member

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    The onboard computer is more accurate than filling the tank and calculating. Just reset it everytime you get gas, along with the trip odometer.
     
  12. jammin012

    jammin012 The man behind The Man

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    New fill up data and LOOK AT THAT.... down to $2.95/mile. That's 10c in 1 fillup. This car rocks.
     
  13. carz89

    carz89 I study nuclear science...

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    Not exactly true.
    The onboard computer is more accurate for a single fillup. But over time, manual calculation will be more accurate. I have kept a weighted average of both methods for over 10,000 miles, and the MFD calculation is 2 mpg higher than the manual method.
     
  14. COMP

    COMP New Member

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    i'm not surprised
     
  15. PriusSport

    PriusSport senior member

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    You have to go by the consumption readout. The tank gallons to fill is inaccurate on this car because of the bladder. It is more accurate on other cars I have owned with an on-board computer.
     
  16. carz89

    carz89 I study nuclear science...

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    Again, not entirely true. Yes, the bladder issue causes inaccuracies when doing the manual calculation on a single tank. But over numerous fillups, the manual calculation will be more accurate, regardless of the bladder issue. Use GreenHybrid - Interactive Hybrid Cars Resource to help you keep tally, or create your own spreadsheet.
     
  17. RhythmDoctor

    RhythmDoctor Member

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    The bladder fluctuation applies to individual fillups - it disappears over the cumulative effect of multiple fillups. Total cumulative miles divided by cumulative gas purchased will always be the most accurate metric over 10 or more fillups.