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Bad mileage, bad gas, car computer adjusted??

Discussion in 'Gen 2 Prius Fuel Economy' started by J_w73, Oct 22, 2009.

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  1. J_w73

    J_w73 Junior Member

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    ok.. I've had my car for about a month and put almost 3000 miles on it.. (I know.. YUCK!!)
    Anyway.. I have been averaging about 51-54 mpg through a tank according to the MFD. When I calculate by miles driven and how much gas I put in it seems to be around what the mfd says or alittle better..( I know this is inaccurate with the fuel bladder being in these cars).
    Anyway, my last fill up at Shell I reset the mpg and did my drive to work. I noticed the mpg being low and it being difficult to achieve the higher mpg stretches. The weather was really really windy and rainy that day so I just attributed it to that.. Well I just got through the rest of the tank and it didn't get any better..I was about 42 mpg with 3 pips left and the gas mileage started to get better as it usually does with less fuel in the tank (lighter car / higher mpg??) Today I had 1 pip left so I decided to fill up. The final MFD mpg was 47.1... going 360 miles..(I normally get around 450 miles on a tank) When I computed it with the gas I put in (8.7 gallons- seams to be around the norm) it came out to 42 mpg.

    Just drove my normal route home on the fresh tank (no Shell gas) and got a record 61.1 mpg on the MFD. Best before that was 54 mpg.

    Questions and facts..
    The Shell station sold E85 gas also.. I didn't use the E85 hose but is it possible they put E85 in the wrong tank either on purpose or mistake?

    If so, will the computer adjust the performance of the engine based on the power/energy of the fuel..?

    Would this explain my average mpg going from 42 -47 mpg in less than 100 miles or my 61.1 mpg on my ride home with the new tank?

    I would say the outside temperature was a little colder than normal during that tank.. nothing extreme though.. around 55-65 instead of 65 - 80..
    on the drive home it was around 79...
     
    #1 J_w73, Oct 22, 2009
  2. qbee42

    qbee42 My other car is a boat

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    Cold weather and fuel formulations could easily account for your mileage variation.

    Tom
     
    #2 qbee42, Oct 22, 2009
  3. uart

    uart Senior Member

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    "The Shell station sold E85 gas also.. I didn't use the E85 hose but is it possible they put E85 in the wrong tank either on purpose or mistake?"

    Very interesting. Maybe you should try a tank of E85 in it some time just to see if it gives you the same low MPG as that last tank. I'd be indterested to know the results anyway. :)
     
    #3 uart, Oct 23, 2009
  4. F8L

    F8L Protecting Habitat & AG Lands

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    The really windy and wet day basically screwed up your tank. Because it is an average of your total MPG for that one tank you cannot overcome driving in such conditions unless you started hypermiling to artifically inflate the numbers left on that tank to get close to your normal average.
     
    #4 F8L, Oct 23, 2009
  5. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    The Prius is NOT a flex fuel car. I would not do this.
     
    #5 JimboPalmer, Oct 23, 2009
  6. philobeddoe

    philobeddoe ΜΟΛΩΝ ΛΑΒΕ

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    i hope this isn't too off topic, but i am modding my gen ii to run on hazelnut oil and bald eagle heads :thumb:
     
    #6 philobeddoe, Oct 23, 2009
  7. uart

    uart Senior Member

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    Hi Jim, does E85 refer to 15% ethanol or (yikes) 85% ?

    We don't have E85 in Australia, I think I wrongly assumed that must have been 15% ethanol when it's really 85% ethanol. Is that right?
     
    #7 uart, Oct 23, 2009
  8. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Yes, E85 is 85% Ethanol, 15% gasoline (petrol)
    It would only have 70% of the energy of pure gas, so would get less MPG, but the plastic parts of the car would need to be designed for Ethanol, as it may be a solvent to materials in the fuel system.

    Most cars in the US run fine on E10. (10% Ethanol)
     
    #8 JimboPalmer, Oct 23, 2009
  9. J_w73

    J_w73 Junior Member

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    Thanks for that info...
     
    #9 J_w73, Oct 23, 2009
  10. J_w73

    J_w73 Junior Member

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    so why the 61.1 mpg on my trip home with the fresh tank??

    I have never averaged that much on a trip to or from work..
     
    #10 J_w73, Oct 23, 2009
  11. Bob64

    Bob64 Sapphire of the Blue Sky

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    Because the car was already warmed up when you finished filling your tank.

    Warmed up car = not as much fuel spent warming it up again. Also has the benefit of immediately entering Stage 4.
     
    #11 Bob64, Oct 24, 2009
  12. J_w73

    J_w73 Junior Member

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    Well I got through that tank and the computer said 54.3 , a new record for my for a tank..
    and as far as distance I went 476 miles which is also a record.. last pip never started flashing
    476 miles on 8.3 gallons.. showing 56.8 mpg..
    and again I know this isn't accurate but I seem to always be putting in around 8.3 to 8.6 gallons on every fill up from 1 pip left..

    so on the trip home on this fill up I put up a 64.6 mpg according to the computer.. another new record..

    I'm not sure what is going on but I like the increased mpg..
     
    #12 J_w73, Oct 26, 2009
  13. Celtic Blue

    Celtic Blue New Member

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    It's easy to get mileage that high after warm up and a tank fill depending on the remainder of the commute. In warm weather we can get 99.9 mpg for the two miles from the station depending on traffic.
     
    #13 Celtic Blue, Oct 26, 2009
  14. J_w73

    J_w73 Junior Member

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    I guess I should have mentioned I am driving 50 miles on the freeway home..

    If it is all about the car being warm the gas station is right by the free way .. so whether I stop and get gas or don't the car should be warm either way when I get on the free way.. so I should have been able to get that mileage in the past...
     
    #14 J_w73, Oct 27, 2009
  15. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    Here's my impression of what happened on that bad tank: you got off to a bad start. Period. That's it. Over the tank average, it's much easier to ruin a high number than to improve a low one. With the wind, the rain, and the dropping temps, your mileage will drop.

    I will refer you to the <Current Mileage> link in my signature. You will find a record for every tank I've consumed over the last five years. My mileage goes down predictably every winter.
     
    #15 TonyPSchaefer, Oct 27, 2009
  16. J_w73

    J_w73 Junior Member

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    ok.. that is fine but why didn't I get the booming mpg that I am getting now last month when it was 90+ degrees out?.. same drive.. same AC on low.. same everything..
    its been about 80 degrees the last couple of weeks..
     
    #16 J_w73, Oct 27, 2009
  17. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    well i have same problem except in reverse. the other day, i filled up, did a few errands and by the time i got home, i was at 75 mpg....that has dropped daily and now with 4 bars left i am at 59 mpg...it does seem to be holding.

    what happened?? ... then again. never mind.

    in a car that maximizes efficiency, the first thing we need to understand is that

    EVERYTHING MAKES A DIFFERENCE.
    * Season... gas formulation changed thru-out most of the country within the last few weeks
    *temperatures
    *weather (rain on the road increases rolling resistance. in heavy rain, i lose 2-4 mpg on my short trip to work)

    *lights. as soon as the time changes, i will have some quantifiable numbers. not saying for sure, but it does appear that the difference will be measurable.

    *and then the BIGGIE....**DEFROST**, now heat does to but to a much lesser degree. heat only slows down how fast your car gets to its optimum running temperature.

    but like i said, everything makes a difference
     
    #17 DaveinOlyWA, Oct 27, 2009
  18. EZW1

    EZW1 Active Member

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    Yup. I was easily getting 63 t 65 on my '09 but this morning the temp was down to 50F and I found I had to finesse the car to maintain 63. If this winter is going to be like last winter, then when it gets colder I'll be lucky if I can get 55.
     
    #18 EZW1, Oct 27, 2009
  19. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    u have "winter" in Phoenix?
     
    #19 DaveinOlyWA, Oct 27, 2009
  20. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    Here's your answer.
    Give it time, young padawan. The reason you are turning out record tanks now is that you are learning about driving the car and the car is learning about how you drive it. Shoot, I didn't crack 55mpg for almost a year.
     
    #20 TonyPSchaefer, Oct 27, 2009
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