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Trying to figure out what my MPG should be

Discussion in 'Gen III 2010+ Prius Fuel Economy' started by NargilFenris, Jan 10, 2012.

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  1. NargilFenris

    NargilFenris Junior Member

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    2011 Prius
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    I am trying to figure out what my mileage should be about right now and what it will be once the car finishes breaking in and the temps warm up.

    - Have you read This Thead Yet? - Yes

    - What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations) - 38 manual

    - What fuel economy are you expecting and why? - Mid 40s. Mixed driving, high highway speeds, winds(wind speed is typcially around 10 mph but jumps to 20 or more very often), cold weather, breaking in new car.

    - What are the approximate outside air temps? - Ranging from 60s to 20s currently

    - How long are your trips? - ~30 miles @ 45 mins

    How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? (Method Here) - Less than a month.

    Have you had your alignment checked? Any pulling or abnormal tire wear? - No, no.

    - How much of it is city vs. highway? Roughly what's the average speed in overall and and of each segment? Is there a lot of stop and go driving? First 5 mins is city, followed by 65 MPH highway for 10 mins, then tollway at 75 MPH for 15 mins, 65 MPH highway for 10 mins, ending with 5 mins of city driving. Very little stop and go maybe 10 mins at the most.

    - What's the terrain like of your drives? (e.g. flat, gentle hills, steep hills, etc.) - Terrain is mostly rolling hills.

    - What are your tire pressures? - 40psi all around

    - Is your oil overfilled? (i.e. above the full mark on the dipstick) - No

    - Make, model, year, engine and transmission of previous car? (e.g. 08 Honda Civic Si 2.0L 4 cylinder, manual transmission) What did you actually get on the same trips/commute? (Please give us actual numbers, not EPA ratings.) - 2004 PT Cruiser 2.5 automatic, we averaged around 18-22 mpg

    - What region/state are you in? (if you haven't set your location) - Lawrence, KS commuting to Topeka, KS

    - How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking? - Brisk acceleration to get to speed since I am mostly doing highways/tollway. I do gentle braking.

    - What modes are you using, if any? "normal", EV, power, eco? - Normal mode except when leaving/entering my apartment/parking garage at the start and end of each trip when I try to use EV if car is warm enough.

    - Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on? - No I use accessory mode since I only need 2 mins to scrape off my car.

    - Are you driving using D or B mode? - D mode.

    - HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to? - I use the heater since my wife gets cold easily. I set it to about 75 for 5 mins then drop it to 68 and place on auto for the rest of the trip.

    - Are you using the factory tires and wheels? If not, please indicate tire make, model and size (e.g. Goodyear Assurance Fuel Max 185/65R15). - Factory tires.

    - Other. - I have the upper grills block currently and I still need to cut the rest of the foam for the lower grills for the days it gets really cold.
  2. Gurple42

    Gurple42 New Member

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    B mode is only for engine braking on long downhill grades, not for anything else. My guess is that your use of B mode explains your low mileage. Hope this helps:)
  3. stevemcelroy

    stevemcelroy Active Member

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    In Kansas you likely would never need to use B - use it the same as you would use low on a regular automatic. The other piece of advice would be to stop thinking about mileage so much - just drive it normally, same as if you had a Civic and wanted to maximize mileage.
  4. fuzzy1

    fuzzy1 Senior Member

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    Looking at a topo map, I see a total elevation change of less than 300 feet, and only shallow hill slopes. You have no reason to use B mode. It hurts mpg in city traffic, and does nothing on the highway (unless your driving style including pulsing the gas pedal, in which case it will hurt on the highway too).

    While the 75 mph section hurts, it should still allow mid-40s mpgs. But the wind, if it blows all the time, is costly.

    Setting the climate control to 75 for the first 5 minutes, when the outside temperate is in the 20s, definitely hurts while the car is warming up. If you can reduce or delay that setting until reaching the 65 mph road, it should help a bit. But you may just have to write this off as a cost of keeping the wife happy.

    How many tanks of fuel have you used in this new car?

    While getting accustomed to this new car, make a habit of resetting one of the trip meters when starting the car each morning, or even each direction of your commute, so you can get faster mpg feedback. This helps to refine your driving habits faster. The MPG reading will start out pitifully low, even single digits, as the car warms up, but this doesn't matter. The number will increase throughout the commute (except maybe during the 75 mph section), and should reach its maximum at your destination. This is the number that matters. And you may find that wind causes one direction of the commute to read much different than the other.

    And don't cheat by waiting a minute or two after starting to reset the trip meter. Well, you can, and it will read much better this way, but the results will never be comparable to the readings from truly cold starts.
  5. NargilFenris

    NargilFenris Junior Member

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    Ok I guess I missread some of the info on when you should use B mode. I should mention I never use it during my daily commute, I just used it when driving around town with a few of our hills.

    The wind is always blowing around here. It is weird when it is blowing less than 10 mphs.

    I don't worry about using a little extra gas for keeping the wife happy.

    I am just trying to figure out about what I should be seeing with a car getting broken in, with the cold, the winds, etc.
  6. bisco

    bisco cookie crumbler

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    i don't think breaking it in will help much. stay out of b mode for a tank and see where it goes. if that doesn't get you into the 40's, you'll proly have to slow down on the highway. most people get high 40's low 50's in normal driving.
  7. Teakwood

    Teakwood Member

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    On the Gen III Prii, you should be blocking the lower grill, NOT the upper. this is different than the Gen II.
  8. SageBrush

    SageBrush Senior Member

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    Check out this software simulator form Wayne Brown. He is one of the seminal Prius hackers of all time, and all-around genius to boot.

    To answer your question -- yes, most of your low MPG is explained by the cold, your driving speeds, and the wind. B mode use has not been helping.
  9. xpcman

    xpcman Active Member

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    I would not bother with the EV mode use. It only works when the car has warmed up.
    The grill blocking is a good idea - I would only block half the lower grill unless a bought a scangage to monitor the temp.

    As the tires break-in (500 miles or more) you should get around 40-42 MPG winter and 50-52 MPG Summer.
  10. Zanrok

    Zanrok Casual Prius Lover

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    which battery is running the accessory mode? Could that be hurting his mpgs as well?
  11. NargilFenris

    NargilFenris Junior Member

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    I started with the upper grille because I heard it helps with the aerodynamics which considering the highway speeds around here I thought was a good idea. That and it was cold and windy as hell the day I was outside working on it.
  12. Joe166

    Joe166 New Member

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    That shouldn't make any difference. Whether it is the 12 volt or main battery it still has to be charged up from somewhere, which, barring a solar panel or two, means from the main propulsion battery or the engine running or regenerative braking. Any of those cost energy, which eventually "hurt" mpg.

    I bet the use of "B" mode is the main culprit.

    I bet most people never use "B" mode at all.
  13. rogerv

    rogerv Senior Member

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    Thank you for your service in the U.S. Coast Guard. (What coast are they guarding in Topeka, Ks. ? :D)
    I don't see any mention of your using "B" mode in your original post, yet several following posts blame that for your mileage.
    My daughter bought a 2011 with level 2 trim, and reports getting around 48 mpg in and around Cinncinatti and Northern Kentucky, with a similar commute time to yours. She now has about 5K miles on it, but has so far had mild winter weather and temps. She found that leaving the selector in "normal" gets her the best mileage.
    One suggestion would be to back off on the loud pedal a bit on that toll road. You can watch the instant mpg readout to see what that added ten miles per hour is costing you in fuel consumption. Good luck.
  14. fuzzy1

    fuzzy1 Senior Member

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    Compare the timestamps on those posts to his most recent edit timestamp.
    1 person likes this.
  15. rogerv

    rogerv Senior Member

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    Ah, now I see where he probably changed it. The question now is whether it was a typo originally, or has he actually been running in "B" mode all the time?:eek:
  16. NargilFenris

    NargilFenris Junior Member

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    The USCG has a pay and personnel center in Kansas. It was moved there in the 70s when pay checks were mailed out. They figured with it in the middle of the country everyone will get their checks faster, not that it matters now with direct deposits.

    I orignally had on there that I used B mode because I had used it for messing around town. I never actually used it on our commutes.

    As for toll road the speed limit is 75 and like most places if you dont do the speed limit your liable to be run off the road.
  17. Joe166

    Joe166 New Member

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    I have found an incredible drop off for every mph over 50 or 55. When I drove to the Georgia line from Miami on turnpike and interstates I never broke 40mpg until I got to where I was going because I was in a hurry, but when I drove from Miami to Key West, on US1 which has varying speed limits but basically tops out at 55, I was over 50mpg. HUGE difference. Especially if you are trying to keep up with traffic to avoid bullet holes in the side of the car as we have to in South Florida.
  18. cwerdna

    cwerdna Senior Member

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    http://priuschat.com/forums/other-c...eage-no-its-your-gallonage-really-counts.html
  19. tedjohnson

    tedjohnson Member

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    For cold weather, turn off the heat/fan until the engine temp hits 150F (if you have not instrumented for that with a scangage just wait for 3 minutes of driving ) then it is ok to use the heat. Block only the bottom grill openings , not the top , unless you instrument the Inverter temperature. Use slight rises in the road to pulse and glide a bit . Keep your built in instrumentation on HSI and learn what the different sections of the display show you. Tires should be at 44 psi. Once you get the hang of how this car drives, you can easily get winter mpg's in the 50's, summer in the 60's even running snow tires. These are great cars capable of much better than the EPA specs, but it takes a while to get the hang of maximizing your MPG. That stretch of 75 mph will drop you maybe 3-4 mpg on your commute. If you get into how it works, adding a Scangage helps you to keep the engine HP at about 20 when you need the engine, and lets you coast using elec to propel you when the engine is not needed for drive. After a while it just becomes second sense and your yearly mpg will go way up..
  20. cwerdna

    cwerdna Senior Member

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