MPG on cross-country road trip

Discussion in 'Gen 3 Prius Fuel Economy' started by gboss, Oct 1, 2021.

  1. gboss

    gboss Junior Member

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    I'm on long trip across country and thought I would post my results. I've been driving relatively modestly, but not hypermiling by any means - basically just riding EV whenever I can, using ECO mode on highway, pump and glide down hills 50% of the time. I don't have the tire specs on me, but I am running lower profile tires (std for the premium wheels of the Prius five) at Toyota's suggested psi .

    • NYC --> DC: 52 mpg (avg for entire trip). I really took it easy and used ECO mode the entire time. No AC. I'm really surprised I didn't get more, I've heard that 55 mpg is easy if you pump + glide, have an easy foot, and average 55 mpg.
    • DC --> Charleston, WV --> Lousville, KY --> Nashville, TN --> Memphis, TN --> St. Louis, MO --> Kansas City, MO: 47 mpg (avg for entire trip). Not as conservative w/ gas pedal (highway speeds of ~ 65mph) and used AC 60% of the time.
    • Kansas City, MO --> Dodge City, KS --> Boulder, CO : 45mpg (avg for entire trip). AC here and there but definitely gunning it more often across KS and up mountains in CO. I did have one night sleeping w/ the AC to keep moisture down during a severe storm, but outside temp was relatively the same as what the inside was set to.

    I know for a fact a few things contributed to the reduction in mpg: the rolling hills of Kentucky and WV, STRONG headwinds along most of the Kansas prairie, and having to gun it up mountains in Boulder, CO. Are these results decent for a 2013 w/ ~75k miles?
     
    #1 gboss, Oct 1, 2021
    Last edited: Oct 1, 2021
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  2. drbtz

    drbtz Junior Member

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    In my opinion they're great results for US interstate speeds and factoring in uphill climbs. Really solid numbers.
     
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  3. dig4dirt

    dig4dirt MoonGlow

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    +1 I'd say pretty good results.
    On par or actually slightly better with the low profile and (17" wheels maybe?)

    The only time I could achieve better results were back roads and if no one was behind me :LOL:(y)
     
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  4. farmecologist

    farmecologist Senior Member

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    Strong headwinds are a MPG killer for *any* car. That combined with freeway speed limits of 80MPH in some states can absolutely decimate MPG.

    Personally, we have seen this frequently on road trips in areas like the high country of Wyoming. A couple times the headwinds were so strong that folks on motorcycles had to pull off at a rest area. In fact, it affected MPG so much that *nobody* was going the posted 80MPH. The MPG in our Prius took a hit...but I'm sure the folks in the big SUVs/Trucks could actually see their fuel gauge go down in real time. :ROFLMAO: Another fun observation from these trips...many folks were not going the posted 80MPH even *without* headwinds. I suspect they realized doing so would really degrade their MPG.
     
  5. gboss

    gboss Junior Member

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    :ROFLMAO: true dat
     
  6. brzy25

    brzy25 New Member

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    Sounds pretty good. My commute is 80 miles a day highway and I only get around 42mpg on a tank when I drive at 70+ keeping up with traffic. I've been trying to go easy on this tank by doing 65 and taking a slower route where I can run all electric on the service road for a few miles and I'm sitting at 47. A/C I leave at auto 74 with bursts of the ion filter when I want more air.
     
  7. privilege

    privilege Member

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    over 55mph the efficiency tapers off quickly.

    what octane fuel were you using ?

    ethanol or real gasoline ?
     
  8. gboss

    gboss Junior Member

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    That’s pretty comparable. 47 sounds about right given those speeds. I’ve been fortunate that I can take things slower at around 60-65 on the highway. I’ve also noticed that it really helps going slower up hills and then coasting down the other side of the hill, it doesn’t seem to disrupt traffic to do it this way as long as you were in the slow lane when you’re climbing.
     
  9. gboss

    gboss Junior Member

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    I’m just using regular 85 octane fuel. It seems a little counterintuitive, but I’ve noticed the car is at its best at around 60 to 65, any slower and the engine seems to work just as hard if not harder to maintain the same speed. I do understand irresistible and how anything over 50 to 55 mph generally reduces efficiency, but for some reason the momentum of this car seems to play a major role add around 60 to 65
     
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  10. drbtz

    drbtz Junior Member

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    It has certain bands it favors for whatever reason. I'm not an engineer so I couldn't tell you but one of those bands is around 42mph where the mog tapers off but improves slightly around 47mph before dropping back off.

    Someone had a fantastic chart on it but I can't find it atm.
     
  11. fuzzy1

    fuzzy1 Senior Member

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    It is right here, but the image has been missing since a website update last year. Maybe @bwilson4web can refresh us?:
    Updated MPG vs MPH chart | PriusChat

    While the curve was a bit bumpy, I don't recall it improving with increasing speed anywhere. It was a strictly monotonic decreasing curve.
     
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  12. drbtz

    drbtz Junior Member

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    Correct, I apologize I mispoke. The drop in mpg was more pronounced between 39mph and 46mph (IF I remember correctly).
     
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  13. gboss

    gboss Junior Member

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    I am now at 4300 miles and averaging 46.2 mpg for the entire trip. Up and down Colorado Rockies, through Utah national parks, and mostly highway speeds.

    It seems that the mpg gains while coasting outweigh the losses from climbing mountains oddly.
     
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  14. gboss

    gboss Junior Member

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    • NYC --> DC: 52 mpg (avg for entire trip). I really took it easy and used ECO mode the entire time. No AC. I'm really surprised I didn't get more, I've heard that 55 mpg is easy if you pump + glide, have an easy foot, and average 55 mpg.
    • DC --> Charleston, WV --> Lousville, KY --> Nashville, TN --> Memphis, TN --> St. Louis, MO --> Kansas City, MO: 47 mpg (avg for entire trip). Not as conservative w/ gas pedal (highway speeds of ~ 65mph) and used AC 60% of the time.
    • Kansas City, MO --> Dodge City, KS --> Boulder, CO : 45mpg (avg for entire trip). AC here and there but definitely gunning it more often across KS and up mountains in CO. I did have one night sleeping w/ the AC to keep moisture down during a severe storm, but outside temp was relatively the same as what the inside was set to.
    • Boulder, CO --> Grand Junction, CO --> Arhces NP --> Zion NP --> Bryce NP ---> Salt Lake City, UT : 46.2mpg (avg for entire trip). LOTS of mountain climbs in Colorado & Utah. Sleeping every night w/ the AC to keep moisture down. Outside temp was relatively the same as what the inside was set to. ECO mode as much as possible, gliding down hills, but still maintaining ~65mph on highways. Mostly highway miles overall on this trip.

    Seems like I can't update OP, so I'll just keep an updated log with new posts. Already at ~4,100 miles for this tripe - sounds like 46.2 mpg ain't too bad for this type of driving.
     
  15. fuzzy1

    fuzzy1 Senior Member

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    I find that "it depends", varying by circumstances. It works on some roads, but not all. Shallow descents, allowing considerable coasting or gliding or even just reduced power cruising, can do this, if the driver style allows. Steeper descents demanding significant amounts of energy-wasting braking, don't.

    Note also that high elevation cruising also benefits from the reduced drag of the thinner air, compared to sea level. And the difference is not negligible. Additionally, Otto-cycle engines are more efficient (but less powerful) at high altitude due to less 'pumping loss'. The Prius Atkinson-cycle engine benefits less from high altitude because it has already clawed back a decent portion of this loss mechanism at all altitudes.

    Note that your shouldn't simply average MPGs of different trip segments, as this will slightly exaggerate your overall trip MPG. The proper math is to divide total trip distance by total trip fuel consumption. For small differences in trip segments, the error is negligible. But when averaging uphill and downhill segments together with large MPG differences, the error can be significant.

    Note also that some here will very hotly dispute that gliding downhill can ever come close to making up for the uphill climb, that such is a violation of the laws of physics. But they are ignoring several real factors.
     
  16. gboss

    gboss Junior Member

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    The mpg I am quoting is for the total trip, not individual segments. I am showing various segments of the trip to note specific environment/trip factor that could contribute to a rising or lowering total mpg.

    Really interesting things you are pointing out - I’ll have to read up more on the Atkinson-cycle as it relates to altitude

    Yeah, the folks that argue against downhill never makes up for uphill would be ignoring the range that EV can enhance a coast on gradually flattening downhill and flat land after the descent. It’s basic physics, they would also be correct in other circumstances.
     
  17. privilege

    privilege Member

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    yuuuuup. mine seems to like about 45-55 mph for top fuel economy... any lower and it needs to use "pwr" mode too often. any higher and the wind starts to make a big play.

    I'm guessing the terrain is effecting it also
     
  18. gboss

    gboss Junior Member

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    I'll also add - I've been running the heat at night (all night) for the past few days since I am now up North where it is snowing and the average mpg goes down 0.2 each night (currently at 46.1mpg for 4800 miles). The gas guage doesn't move :)

    This car is growing on me. Incredible machine.
     
  19. drbtz

    drbtz Junior Member

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    Haha I felt the same way. I had to stay overnight in Chicago in 95°F weather. I ran the car overnight to use AC at a moderate temp. At that moment I fell in love with the truly interesting and amazing machine Toyota created.
     
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  20. gboss

    gboss Junior Member

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    Well said . The Prius definitely has to be put to use and experienced to be truly appreciated.
     
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