Is 50 mpg at 65mph normal?

Discussion in 'Prime Fuel Economy & EV Range' started by White 17, Feb 27, 2017.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    One thing I read about but don't have the citation is tire resonance leading to higher drag. At higher speeds, a tire can setup a resonance that increases the rolling drag and tire heat. This is a complex phenomena but making the tires 'stiffer' with higher pressure should reduce this effect.

    Bob Wilson
     
  2. 65mpg_utahn

    65mpg_utahn New Member

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    I always buy Costco gas and can get 65 mpg in town and 52 hwy. I don't have much of a lead foot I like to ease onto the freeway.
     
  3. Michael Nielsen

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    I have logged around 2,500 miles on a road trip from Delaware to Arizona, generally driving at 70 mph with a passenger and our stuff. 46 mpg.
     
  4. bwilson4web

    bwilson4web BMW i3 and Model 3

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    You might consider adding to our knowledge using one of your trip meters:
    • Wait 20 minutes into a first drive, 5 minutes on subsequent drives - to warm-up the car.
    • Set your cruise control speed, dynamic or ordinary.
    • Reset the trip meter and note the location (longitude/latitude is perfect) but City/State is good enough
    • When ready to pull off, note or photo the trip meter and note the end location
    • Record head-wind, tail-wind, and approximate strength and temperature but we can look up the weather records closest to your route
    We can use the one-way, benchmarks to compare against the mph vs MPG chart. Not perfect, good enough to help everyone understand what the car does. This approach removes the warm-up penalty and helps account for weather, temperature, and altitude changes.

    Bob Wilson
     
  5. bisco

    bisco cookie crumbler

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    those charts are great, thanks bob. any chance of a simple mpg vs tire psi chart for the great unwashed?
     
  6. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I wish there were but it is not that simple because we still have to deal with all of the other variable: fuel, warm-up, temperature, e.t.c. But there may be a way to indicate a percentage improvement. Let me think about it for a bit.

    Bob Wilson
     
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  7. James Wells

    James Wells Junior Member

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    1,800 mile drive from Austin to NYC. 54.3 mpg freeway at 70-80.

    Posted via the PriusChat mobile app.
     
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  8. MattStevenson

    MattStevenson Member

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    Ambient temperature plays a huge factor but basically anything above 55mph is wasting gas. Airpressure on the front of the car builds drastically above that speed. That's why many states had a max speed limit of 55mph for a long time.

    Posted via the PriusChat mobile app.
     
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  9. thatoneraccoon

    thatoneraccoon Active Member

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    I also wonder after the ice fully breaks in and looses up a bit, if then mpgs get better

    Posted via the PriusChat mobile app.
     
  10. bisco

    bisco cookie crumbler

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    seems like a dyno in controlled conditions would be the best way?
     
    #30 bisco, Feb 28, 2017
    Last edited: Feb 28, 2017
  11. bwilson4web

    bwilson4web BMW i3 and Model 3

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  12. White 17

    White 17 Junior Member

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    I haven't checked the prime but another car I have is about 10% high on the dash MPG readout compared to using a calculator. It is hard to do with the battery mixed into the equation. Perhaps we should be using some sort of correction when using the MPG readout.
     
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  13. bisco

    bisco cookie crumbler

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    on the pip, it gives you hv/ev miles on the trip meters. makes for an easy calc at the pump. is there any way to do it on prime?
     
  14. White 17

    White 17 Junior Member

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    I haven't found that yet.

     
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  15. bwilson4web

    bwilson4web BMW i3 and Model 3

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    #35 bwilson4web, Mar 4, 2017
    Last edited: Mar 4, 2017
  16. White 17

    White 17 Junior Member

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    I did a 600 mile trip this week and kept track of the hand calculated and trip meter readings. I started with a full tank and nearly zero charge reset the A and B trip meters. I filled three times and reset the B trip meter each time.

    First fill up calculated at 56.5 mpg and B trip meter was 59.2 mpg or about +2.7 miles/+4.8%.
    Second fill up calculated at 62.0 mpg and B trip meter was 61.7 mpg or about -0.3 miles/-0.5%
    Third fill up calculated at 54.8 mpg and B trip meter was 57.6 mpg or about +2.8 miles/+5.1%
    Total for trip calculated at 57.1 mpg and A trip meter was 59.1 mpg or about +2.0 miles/+3.5%

    I almost had a pattern there but the one check kind of messed up perfect. Right now it seems like it might be the meter reads two to three miles over. I will try it again next week on another quick trip I have planned.

    Also, I suppose it really doesn't matter about the battery charge EV miles added as that is still going to be on the trip meter calculation and should compare to the hand calculation. I would make a difference if I wanted the gas MPG only. I guess that is poorly said but anyway.

    As to the actual mpg numbers they are better than I was getting before. Speed was mostly over 50 and no more than 65. Can't explain it but I shouldn't complain either.
     
  17. pricoaster

    pricoaster Member

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    On the Drive Monitor screen, it will show you the EV Driving Ratio based on the current trip monitor you have selected (ODO, Trip A, Trip B or since Last Start). By multiplying this percent by the miles logged in the trip monitor, that'll give you the miles driven in EV mode and the difference is the miles driven in HV mode.

    For example, the attached pic shows Trip A (since my last visit fill-up at the gas station, which was on Feb 4th). I've driven a total of 1,017 miles, with a 76% EV driving ratio, meaning I've driven about 771 miles in EV, and 243 in HV. I didn't take a pic, but the distance to empty is around 220 miles. And I have about a half tank left, so it's generally accurate.
     

    Attached Files:

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  18. Lee Jay

    Lee Jay Senior Member

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    Has anyone ever taken a look at the "Eco-Diary"? Last one under drive information.
     
  19. Lee Jay

    Lee Jay Senior Member

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    Also, why do people assume the gas pump is ground-truth? It's not. The pump can be off and you are dividing by miles accumulated on the odometer, which can also be off.
     
  20. Mendel Leisk

    Mendel Leisk Sand Pounder

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    I do because the laws of the land come down hard on both those, if they're off.
     
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