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You will not get 50 MPG if...

Discussion in 'Gen III 2010+ Prius Fuel Economy' started by wfolta, Aug 2, 2009.

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  1. wfolta

    wfolta New Member

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    None of this means you're a bad person. It's just meant to give some thoughts on why you might not be getting EPA mileage (or better) in your driving. As the ads say, YMMV, and even if you don't achieve EPA, you're probably getting better mileage -- for the same geography, climate, weather, and driving style/habits -- than any other car you might choose. For your consideration, you probably won't get 50 MPG if...

    1a. You drive 5 miles to work. The car gets relatively low mileage while warming up, so you take a big mileage hit at the start of every trip, and need to run long enough to overcome that initial deficit.

    How far do you have to drive to get 50 MPG? As one example, I drive 11 miles to work in a mixture of city, open highway, and stop-n-go backed up highway, and get 50 MPG without much trouble.

    1b. You drive a bit farther than 1a, but you "warm up" the car for several minutes before driving. ("Warming up" is getting 0 MPG, and it doesn't help the car.)

    1c. You drive a bit farther than 1a, but you drive the car hard while it's warming up. (The engine's not getting great mileage anyhow, plus the car will use maximal electric power to keep down the strain on the cold engine, further wasting energy.)

    2a. You stick like glue to the car in front of you, and don't let anyone beat you coming off of a traffic light. If you spend a lot of time in the red "PWR" acceleration zone and brake hard, you'll get poor mileage. Better than you would have if you drove like this in another car, but not 50 MPG.

    2b. You either don't look at traffic ahead, or you do so only to note in the back of your mind that you're going to have to stop up where the red lights are all on. You don't need to leave huge gaps ahead of you, but if you find yourself accelerating towards a car that's stopped/slowing in front of you, you won't get good mileage.

    2c. You never coast. You're either on the gas or on the brakes.

    2d. You spend a lot of time going 75+ MPH.

    2e. You think that Cruise Control gets better mileage than a human driver. (CC only saves gas to the extent that it keeps you from going 75+ MPH. Otherwise, it makes stupid choices.)

    3a. It's winter, or you drive in cold, rainy/snowy weather a lot. (Longer engine warmup, precipitation on the road slowing you.) Or it's summer and you live where it's extremely hot. (High air conditioning use, not in terms of it being on, but in terms of high temperature differentials.)

    Tip: In hot weather, open windows to get the hot air out, then set on manual, recirculate, 78 degrees (if the outside temperature is 80+), with the vents pointing at you at first, then near you afterwards, running the fan at whatever speed seems reasonable. I thought the recommendation to set the A/C to 78 degrees was for mileage-masochists until I tried it.

    3b. You like to drive at interstate speeds with your windows down.

    3c. You go uphill to work, then uphill again to home. :)

    4a. You're so enamored with the fact that you can run on battery-only that you do this as much as you possibly can, mistakenly believing that's why the Prius is efficient.

    4b. You're trying "too hard" to get good mileage, or based on a naive understanding of how the car actually works: running on battery too much, as in 4a. Or accelerating extremely slowly. Or figuring that regenerative braking is really efficient so braking must be a really good way to charge the battery. Etc. (Read the forums for tips on driving truly efficiently.)

    5. You're on your first or second tank of gas. Especially if you measure your MPG by how much gas you put in versus how far you drove, which can be very misleading over short timeframes -- doubly so if you're assuming the dealer filled the tank as you might.

    The car's mileage also increases 10% or so over the first 1,000 miles, as the drive train and tires break in.

    6. You're not sure what the tire inflation is. Most people who get good mileage do so with tires inflated over Toyota's recommendations (though not more than the tire's sidewall), but you don't need this to achieve 50 MPG. On the other hand, if you're assuming that the dealer set it properly and haven't bothered to check it yourself, that could be the issue.
  2. anne1965

    anne1965 Gotta love the game...

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    What I did in my Gen II in winter is switching off the heating for the first 2.5 km. The interior doesn't noticeably heat during such that distance and it will prevent the engine to be kept on all the time because it needs to warm up the interior. It took my first 5-min block from 7.5 l/100km down to 6 or so.

    Now I believe that the Gen II in the US and Europe are different, the US version being more reluctant to shut down the ICE under any circumstance. So this may not have the same impact as on the US version. Since no Gen III's have been driven in real winter conditions, we'll have to see how its fuel consumption responds to interior heating settings.



    Well, I can only accelerate not extremely slowly by going into the PWR area on the hybrid system indicator, which makes the ECO light go out. I suspect the Toyota engineers did that for a reason... So, by avoiding the PWR area, I do accelerate extremely slowly. But that may boil down to a difference in opinion about what 'extremely slowly' is.
    1 person likes this.
  3. alfon

    alfon Active Member

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    My wife drives and she get 46-48 MPG, she does not drive for gas mileage. She drives to get where she wants to go, and back.

    Now, when I drive, my normal style, I get 52-55 MPG, calculated by miles driven and gallons used. I am not a hyprmiler, I drive at or a little above the speed limit.

    Driving style is probably why there is a difference.

    So, if you do not want to get 50 MPG have my wife drive your car.

    alfon
  4. bwilson4web

    bwilson4web 03 and 10 Prius

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    Sometimes it is easier to understand a set of positive guidelines and minimize use of "not." Otherwise, a nice list.

    Bob Wilson
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  5. namasteflc

    namasteflc New Member

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    Has anyone installed an engine crankcase heater for the winter?
    To answer 4a: I try to use EV mode the last 1/2 mile of my journey, through the developement's 25 mph speed limit. I figure that the engine needs to run when I restart the car anyway, so why not let it recharge the battery.
    Frank
  6. Bob64

    Bob64 Sapphire of the Blue Sky

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    Nama,

    Because its busy warming itself up. Its not producing much of any electrical or mechanical power whatsoever. It generates mebbie 10 amps of power, which you can barely crawl to 15mph in 20 seconds if you don't use any battery power.
  7. rahamanmd

    rahamanmd Prius for Change

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    I do the same!
  8. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator Staff Member

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  9. fred garvin

    fred garvin New Member

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    i do this too, just not in EV mode. In eco mode, on the screen showing the ECO light and the zones (not the one with the pics of the motors) i use the gas pedal to keep the indicator just below the halfway point. unless the SOC is way low, this keeps it in battery only up to about 41 mph. I find this works the same or better than the EV mode button.
  10. cossie1600

    cossie1600 Active Member

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    50mpg, I can't even get above 43!
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  11. Felt

    Felt Active Member

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    All good comments with very positive suggestions.

    Cossie1600 - I am sorry that you are not achieving better mileage. I have found fwolta's thoughts to be right-on. I am, by nature, a conservative driver, but certainly not a hypermiler .... my average with 1700 miles on my G3 is right at 53 mpg. To achieve that, it does require some steady driving in the 35-45 mph range (which is possible where we live). I doubt I could achieve that in heavy city traffic, and especially if I did not drive very far (as explained above). I doubt I will do as well come Winter, but I expect to do a bit better when not running the A/C. Thus far, I am absolutely delighted with the Prius.
  12. anne1965

    anne1965 Gotta love the game...

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    The Prius uses battery power in the first stages of warmup to reduce emissions (you know the other emissions than CO2) while the catalytic converter is still cold. Since the prime objective of the HSD program is to pamper the battery, this will IMO increase emissions. I try to use as little forced EV mode as possible and park the car with at least 4 bars of charge.

    Try P&G, that will enable you to shut down the ICE just as much, but without draining the battery.

    Having said that, I have found that in the Gen III it is much harder to maintain more than 3 bars of charge in urban driving.
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  13. seadub

    seadub New Member

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    :welcome: You're not alone.

    I haven't made it near 50 either.
  14. windstrings

    windstrings Certified Prius Breeder

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    Based on where you live, this time of year can be tough... I find the major detractor of gas mileage is if I run the air or heat and how much.

    Either of those plays a big role in how ofter your engine "rests" verses maintaining charge on the battery that the air cond or heater is pulling out.
    You can baby the gas pedal all for naught if you run the air like crazy.

    I get my best mileage during the spring and fall or any time when I don't have to have the air on at all and simply run the fans alone.

    I physically turn off the "air cond" button on the MFD display so only the fans run without the computers logic thinking it needs to maintain a certain cabin temp.

    *No one that is taking a mileage hit has mentioned whether they have the new 17" wheels?
  15. tzor

    tzor Junior Member

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    This is interesting; it's the exact opposite of my experience in my former car (A Gen I 2002 Prius) where the CC saved significant MPG. I'll try using less cruise control. Still, do you really think that CC makes worse choices than a driver actively listening to NPR on his commute to and from work? Guess I'll have to find out.
  16. windstrings

    windstrings Certified Prius Breeder

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    Bad choices by the CC are relative to what its compared to.
    CC can definitely save over people who are always on the gas, and then on the brakes and back and forth and basically don't know how to drive.

    On the other hand, the CC cannot purposely lose speed climbing a small hill because it knows it will regain it again on the other side, or see traffic stopping 400 yards ahead and so start coasting pending whether the light turns green or remains red etc.
    It also cannot do any of the hypermiling or other driving techniques that hybrid drivers have developed to increase gas mileage.

    If I'm on an extremely flat surface, CC is a good way to go if you want to rest your foot, otherwise, it annoys me.

    There is just too much logic the CC cannot see and process that the driver can.
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  17. ancientsan

    ancientsan New Member

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    I'm getting 41 right now....but car not broken in yet (<200miles)...so if I add 10% after break in I'll get 45?
  18. windstrings

    windstrings Certified Prius Breeder

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    If you've never driven a prius before, it could be your driving.
    I feel like my prius started really getting good mileage around 70K or so.
    I"ve always gotten about 45 - 47 with air, 47 - 52 without air.. both driving fast, but I'm pretty good about not doing jack rabbit starts and not using my brakes unless really needed.... those numbers are with my GenII.

    Anytime you get weight moving very fast in a short period of time, that equals lots of energy required.
    Fast top end driving is not what gets you as long as you were pretty gradual in getting there, its the aggressive accelerations that hurt the most as well as unnecessary braking just to have to get up to speed again.... yes the regen saves some of that lost kinetic energy, but its by no means a pure conversion.

    No regen and true "almost frictionless" coasting would be best when letting off the gas, but if Toyota did that, people would have wrecks because they are used to the transmission drag of the older technology cars and trucks and would miscalculate stops etc.

    Once the mainstream of cars are hybrids and that becomes the norm.. maybe that could be... it would be nice to have an option to kill regen when coasting and maintain it for braking IMO.

    But Toyota would have nothing to do with it due to liability issues.
  19. dogllama

    dogllama New Member

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    Spin around 3 times, touch your toes, then move all the change from your right hand pocket to your left....
  20. martinw

    martinw New Member

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    One thing I'm finding is that coasting downhill, even with the regen, the car loses less speed than other cars. I guess it's not that surprising given the aerodynamics, but I thought the regen would cancel it out. I'm finding I spend a lot of time on the brake on long downhills when following other cars that are coasting, even slipperly looking sports cars.



    What happens when the battery is fully charged? I assume the regen system is still operational, so how and when does the extra energy get discarded?