40 mpg...

Discussion in 'Gen 3 Prius Fuel Economy' started by Justin Valle, Mar 9, 2015.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    GOOD POINT!

    It would useful to see how accurate your speedometer/odometer are relative to GPS or highway mile markers..

    Bob Wilson
     
  2. Justin Valle

    Justin Valle New Member

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    Thanks guys, I read everything and appreciate all your advice so much. I just took it into the dealer a second time today to address my mpg issue. The head foreman drove my car 30 miles with me in it and could not make the CONST reading of 40.4 change 1 bit, he kept saying, "I don't know what's wrong, it should change." 2 hours later they got back to me and explained my tires were overinflated and now I'm getting 47mpg which they pointed out on my dash. When I asked the foreman about my 12v, he said as long as it starts its fine, and he also said running the ac has no effect on mpg. The second I drove off the lot my CONST reading began to drop, 50 miles later it settled on 42.1 mpg. I'll check my tire size for an exact tomorrow.
     
    #22 Justin Valle, Mar 13, 2015
    Last edited: Mar 13, 2015
  3. jhinsc

    jhinsc Senior Member

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    Justin, if the dealer foreman can get your average reading up to 47 when he drives it, then when you drive it goes down, your driving style is the likely culprit. You've stated you're not really trying to get good mileage. 2/3 highway but your average speed is only 18 mph? Sounds like stop than go. Driving smoothly, not darting in and out of lanes on the highway, maintaining speed, anticipating when you need to slow down will all help get your mpg average up. In warmer weather, the a/c can affect your mileage, especially when you're stopped in traffic or waiting for a ride because it will use the battery, which then has to be charged up by the ICE. My 2010 Prius IV averaged over 50 all the time, and my Prius v5 averaged over 40 all the time. Now I'm in a VW Passat TDI and get about 42 avg mpg.
     
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  4. bwilson4web

    bwilson4web BMW i3 and Model 3

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    You could run a set of benchmarks this weekend:
    Did you ever try to replicate these benchmark data?
    [​IMG]
    • drive 15 minutes to warm-up car, transmission, and tires
    • find a level highway that you can set the cruise control for 10 miles
      • ideally do a loop
      • alternatively, do two passes, opposite direction
    • record MPG after reaching cruise control speed for a distance of at least 10 miles
      • if doing two passes, reset trip-meter after setting cruise control and average results
    We need one benchmark at or below 40 mph when the car is in 'hybrid' mode. Minimize the electrical loads including AC. Use the windows.

    We need a second benchmark at or above 45 mph when the car is in highway mode. Same as above, avoid extra loads on the car, use the windows.

    Speed is set and managed by using cruise control.

    Bob Wilson
     
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  5. Justin Valle

    Justin Valle New Member

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    P195/65R15 is my tire size

    Bob, I can do a test this weekend, but I'm confused with the logistics; any chance you can give me a link to the long version with all the details of how to run your test? I just learned how to use my cruise control and know the perfect stretch of Interstate 110 -I'm a big fan of legitimate tests with graphs and comparisons and all that, kind of excited even.

    And when I said the foreman got 47mpg and it immediately started to drop when I started driving, I mean PLUMMET, like before I even left the lot, something was very fishy how fast it went down. Also, when we did a test drive together it didn't change at all; he did the 47mpg drive solo but still documented that "customer rode along for 47mpg test drive". I suspect he cheated somehow to get that number.

    And is it true, that running my AC won't affect my MPG?

    Also, if my MPG goes up after I buy this battery, you guys think I have any recourse with my dealership? Still under the 3k mile warranty...
    Yellow top on Amazon
     
  6. bisco

    bisco cookie crumbler

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    he's wrong about the 12 volt, and why don't you ride with him again and have him show you how he gets 47? a/c can knock it down a mile or two.
     
  7. Ashlem

    Ashlem Senior Member

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    If you're doing a lot of stop and go traffic, where you have to do a complete stop, followed by having to accelerate hard, then stopping again a block later, that really saps mpg. But if you hit a string of green lights, then that helps a ton and that's how a lot of folks get high numbers in their prius while doing "city driving". The less momentum you have to lose, the better your mpg will be in the city.

    Like others have said, check the battery as well. Preferably over the span of several days or a week, just to see what kind of readings you're getting, both before you start it up for the day, and at the end of the day. If it's consistently low, you may want to consider replacing it, as it'll give you even more headaches down the road especially if you have to let it sit for a period of time without driving it.

    If you can find out, see how long the prius was sitting on the dealer's lot before you bought it. The longer it was sitting around, the more likely the 12v battery suffered. There have been posts where people said the dealer had to jump start the prius battery before they could even take it out for a test drive since it sat for so long. I think someone mentioned their 12v battery dying after leaving it sitting in an airport parking lot for nearly a month.

    Other things to consider may be that we're still on the winter blend fuel, which gets worse mpg. Weather also plays a huge factor. Though it affects all cars, it's much more noticeable in the prius as a 10% drop from 50 to 45 mpg is much more dramatic than dropping from 22 to 20 mpg in a gas car.

    And if you haven't already, watch this video. Preferably a few times:

     
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  8. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Careful what you ask for: Preliminary 2010 mph vs MPG | PriusChat

    The format of tables changed and I took this opportunity to put them in the new style.

    Now I propose you run a set of benchmarks, one above 45 mph and one below 40 mph. Then vary one variable before repeating:
    • AC off vs AC MAX and coldest setting - crack window if too cold
    • bad 12V battery vs good 12V battery - expect to buy your own replacement as there are more affordable alternatives
    I don't mean the full sweep of speeds. Just one below 40 mph when the car runs in hybrid mode where the engine goes off when it can. Another above 45 mph when the car runs the engine all the time. Then we can compare your data points to mine and begin to understand what is going on by taking out the 'human element.' We want to test the car, not the driver or route.
    That is why it is so important to have a baseline, a valid, trusted set of benchmarks. Comparing yours to mine, we can gain insights to find out if there may be a problem with your car. The key is constant speed managed by the cruise control after the car warms up, ~15-20 minutes. Then make single changes and retest to measure the effect. There could be something yet wrong with your used car but diagnosis becomes a little tricky unless you have something to compare it to.

    I am curious about your 'skill set' and car technology. Do you have a VOM? An existing OBD scanner? A personal tire gauge? Other technical experience with things mechanical? The reason is I want to talk 'with you' and understanding your comfort level. Knowing your background makes it easier when asking for data.

    Thanks,
    Bob Wilson
     
    #28 bwilson4web, Mar 14, 2015
    Last edited: Mar 15, 2015
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  9. Former Member 68813

    Former Member 68813 Senior Member

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    this caught my eye too. this can't be right. 100% hwy should be about 60 mph, 100% city/suburban is about 20 mph. OP, are you sure you actually turn the car off between driving?

    now, my wife actually gets 40mpg when she drives the prius, but she drives aggressively; 80mph, hard acceleration and braking. she even managed to overheat the HV battery once. i tried to reason, but it's not worth the divorce.
     
  10. Justin Valle

    Justin Valle New Member

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    Jhinsc & Bisco - I believe the Toyota foreman cheated the test somehow -I'm guessing they mounted it on those smog test rollers and exclusively used the electric motor. Either way, I've wasted 2 mornings waiting for them to look into this issue with no explanation or even speculation of what is mechanically wrong - they consistently point the finger at me which is understandable, but 40MPG!! I don't drive that aggressively! Anyways, I've lost all trust in their expertise whatsoever; their "highest paid foreman" said that the A/C has no impact on MPG and failed to budge the MPG when I went on a test drive with him.

    Thanks Bob! I'll give it a go THIS weekend. No VOM, don't know what that is. ODB, nope, but I'm getting some ODB-II gadget required by my new insurance sent over soon -supposedly they'll email me if they notice an issue. Personal tire gauge, yes, but I just recently received it and have never been in the habit of checking my tire pressure regularly. I don't change my own oil, I can't install car audio, I don't even work on my PC other than installing memory, so pretty low on the mechanically inclined scale. I'm more graphically/software inclined.

    Ashlem I appreciate your information and insight as well -I have seen the vid before, but thank you just the same. I received a new yellow top that I'll be installing on Saturday, I'll try and find time to run Bob's tests beforehand so I can share the difference.

    Friendly_jacek, I was estimating my highway/city miles based on distance, maybe I was way off. My current average is 20mph. I cruise at about 70mph on the freeway, and I'm somewhere between a conservative-aggressive breaker and accelerator.
     
  11. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Excellent!
    A Volt Ohm Meter (VOM) measures electrical voltage, current, and resistance. If there is a Harbor Freight near by, they often have a nice 7-function unit for $5-8. The best thing is it lets you read the 12V battery and do other useful tests around the crib. <grins>

    We'll make sure you get enough technical details to master the machine.

    Bob Wilson
     
  12. Justin Valle

    Justin Valle New Member

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    I went ahead and installed a new yellow top battery. The voltage readings are the same, and my MPG remains unchanged. I've yet to perform the drive tests because I can't seem to find a suitable place to drive at those speed uninterrupted in LA for such a distance. Anyways, I'm tired of trouble shooting this, after doing some math I've determined the diff between 40 and 50 mpg will only cost me $500 annually, so f-it. After going to the dealer 3 times and thumbing through these forums, it seems most likely that my driving style is the leading factor not the 12V battery like I was hoping.
     
  13. bisco

    bisco cookie crumbler

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    what is the voltage reading? unfortunately, many new 12 volt batteries need to be charged before installing. otherwise, your car has to burn petrol to try to charge it, which it does a very poor job of. it's really designed to maintain a good charge.
    but i must agree with you, you're probably driving it for 40 mpg results.
     
  14. RRxing

    RRxing Senior Member

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    1. Overinflated tires should increase mpg, even if just a little bit (1-2 mpg increase.)
    2. Just because the car starts doesn't mean the 12V is "fine." It needs to be tested.
    3. Running the A/C will have an negative impact on mpg. Again, not much.
    4. Find a new dealer/service department.
     
  15. Easy Rider 2

    Easy Rider 2 Senior Member

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    If that's you in the Avatar picture......yea I can tell that you have a heavy foot. :)
    Doesn't EVERYBODY in LA ???
     
  16. DoubleDAZ

    DoubleDAZ Senior Member

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    Here's my thoughts:
    -- There seems to be a disconnect between the 2/3rds highway claim and the 18 mph average. Just because you're on a "highway" doesn't mean you're driving highway speeds 2/3rds of the time, especially in LA. ;)
    -- The amount my CONS display differs from actual mpg varies greatly, so the CONS display is not a very reliable indicator of mpg.
    -- I can easily increase the CONS mpg by simply driving at or below 20 mph in EV mode. I can consistently get 60-70+ mpg coming home from the gas station because there is a 1/2 mile stretch with speed humps before I get home and I'm usually in EV mode that entire stretch and then the block to my home.
    -- If you force the car to use ECO mode, does it ever use EV mode? I ask because I don't know what happens when you press the ECO button. I use "normal" mode almost exclusively and let the car determine the most effective mode.
    -- I know you said "moderate" acceleration, but I get the feeling it may be a bit harder than that and I'm not sure what using ECO mode does. I know you have to press further to get the same amount of acceleration. A better indicator of acceleration is whether or not the indicator is in the red PWR zone and for how long.
    -- Turn ECO off and go for a 3-5 mile drive with the engine cold, even if it's just around the neighborhood. When you turn the car off, the display shows data for that trip only. It doesn't remain displayed long, so note the data as soon as you turn the car off.
    -- Then go for the same drive with the car warmed up and record the data.
    -- Then do that for longer drives with different traffic patterns, etc., and record the data.

    My mpg is all over the chart. I have over 17,000 miles since July with over 50% of that at average speeds of 60+ mph and my average actual mpg is 45.7, with a low of 34.8 (68 mph) and high of 54.7 (42 mph). I could go into a lot of the variables, like cold weather, rain, headwinds, etc., but the point is to take the time to record the data and see what it shows. I can drive for 30 miles without my CONS changing, so I'm not sure what that shows. I can also take off and see the displayed CONS mpg drop from 50+ to the low 40s very quickly, especially if the car has had time to cool off or the heater is on.
     
  17. DumbMike

    DumbMike Active Member

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    I think the most important thing you've said is that you are in Los Angeles. I've talked to a lot of people whose MPG is normally between 40-42 MPG. Join the club. You wanted to do some of the tests on the 110. Maybe 10-15 years ago you could do that. Not now. If you want to do some testing, here's what I would do:

    Go to the 210 after midnight, somewhere just east of where the 605 meets the 210. Set your cruise control to 60MPH, THEN reset your trip meter and drive to the 15 (or further) and back again. Yes, both ways. It's slightly uphill going east (into the San Gabriel mountains). If traffic is such that you have to take your car out of cruise control, then wait an hour and start again. Try not to change lanes very often. Your MPG should be in the high 50s and maybe up to 60. If not, then something is wrong. That's about as controlled of a test that I can think of doing in Los Angeles. I think it's too hard to do any kind of test doing city driving.

    One other thought: What viscosity of oil are you using? Somebody once said here that if it's 5W-30, or higher, you could be losing some MPG. It should be 0W-20.

    Mike
     
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  18. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Using B mode will be hurting mileage. My advice would be to use it when descending hills with more than 600 Feet of continuous vertical drop, say Cajon Summit on I 15.
     
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