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A tale of two Prius' - Sorry it's long

Discussion in 'Gen 4 Prius Fuel Economy' started by RickyD, May 22, 2022.

  1. RickyD

    RickyD New Member

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    New to hybrids. With high gas prices in Southern California lately, I sold my Cad CTS-V, my Infiniti G35 and EX35. Bought a 2016 Prius 3 tech with 51k miles for $10k and two weeks later a 2016 Prius 2 for $13k with 151k miles. Both pass front doors were damaged, salvaged, and professionally repaired. Both look like new in and out. The 2 has small pits on the front bumper from highway use. The 3 tech is immaculate all around.

    My question is about the MPG:
    The 2 averages 46 - 47, 280 miles on a tank.
    The 3 averages 56 - 59, 540 miles on a tank.
    This is city driving. Highway is better on the 2 with 47 - 49 mpg, the 3 about 59 - 60.

    The 2 is Nimh and the 3 is Li.
    15 tires on the 2 are bridgestones, 17 tires on the 3 are Sentury brand. Air pressure on both cars are at 32 lbs.

    Both cars sold by the same dealer were Toyota serviced all fluids, new tires, brakes, filters, etc.

    I am trying to understand why mpg is so much lower on the 2 than the 3? Mileage difference?

    My scanner shows the 2's traction battery voltages are within spec for each pack. Even stress testing. The battery does discharge quickly when driving but fills back up short of one bar at the top. the lowest the battery discharges is 3 bars from the bottom.

    A Toyota battery rebuilder says don't worry about it and wait for the warning light. in the meantime the 2's mpg is at 47 city driving.

    Thoughts?
     
    #1 RickyD, May 22, 2022
    Last edited by a moderator: May 22, 2022
  2. RickyD

    RickyD New Member

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    I forgot to mention:
    SOC average is 63%.
    12v battery is new.
    All filters are clean.
     
  3. The Professor

    The Professor Senior Member

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    So there are a few things working against the 2.

    The NiMh battery technology performs better than Li in colder climates, which is a reason often cited as to why over here in the UK they lean towards NiMh for many hybrid and electric vehicles, but Li works better when it's not cold. There are a lot of factors here, but generally speaking you'll get greater output from a NiMh battery versus Li at freezing temperature versus room temperature, and they'll charge faster, accepting a higher current. Go down to -10C / 14F and Li really starts to struggle. But that only applies to colder climates. If you're normally driving around when it's above 10C/50F then Li will nearly always perform better than NiMh.

    NiMh is heaver. An equivalent battery pack weighs about 25% more than Li, and those batteries are quite heavy. A quick search on here found someone saying the Li battery is 54lbs (35lbs lighter than the NiMh).

    I don't know about those specific tyres. But I can tell you from personal experience that swapping my tyres made around a 5MPG difference, so it's possible that has an impact too.

    Finally there's the millage. The 2 has done 3x the distance, so it's battery will likely be more worn out.
     
  4. bisco

    bisco cookie crumbler

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    what kind of damage to the doors?

    THIS STANDS OUT
    how are you figuring miles per tank? 280 miles would only be 6 gallons at 46mpg?
    at 56, it's almost 10 gallons

    tires model is important. is 32 all around the door jamb spec?

    li-on doesn't help much, you can see the epa specs for both

    mileage can make a little difference, but not if the car is well maintained. there are a lot of things on a 150k car that need attention, especially the engine and battery. do you know any service history?

    the bttery shouldn't discharge too quickly if you're using the engine, unless going up a mountain.
    it should hover near the middle in most situations except cold engine or stop and go traffic and etc.

    you can get a battery health check with dr. prius
     
  5. CooCooCaChoo

    CooCooCaChoo Senior Member

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    Also the two batteries will behave differently that you may or may not notice. With normal driving, the NiMH battery won't discharge too deeply that's because the battery has optimal life in the range of 60-80% SoC. So the hybrid ECU will keep that battery in that range of charge. The lithium battery on the other hand can handle being discharged more deeply so its operational SoC that the ECU will allow is 20-80%.

    As for the tires, the stock OEM tires are Toyo Nanoenergy. These tires are really good for fuel efficiency and are low rolling resistance. The tires you have on the cars right now may not be LRR tires. This makes a huge difference in fuel efficiency. More than likely the dealership sold you the cars with whatever tires that would allow them to make a profit.

    As for the mpg numbers, the car displays a number that is typically higher than what a calculated mpg would be. If you want to see what you are actually getting, do this:

    1. Fill up the gas tank. Don't overfill once the nozzle clicks off. Either reset one of the trip meters now or take note of the odometer reading.
    2. Drive around for a bit. The more the better because it would be more representative of your average driving.
    3. Fill up the gas tank again.
    4. Math time. MPG is just how many miles you drove on that tank divided by the amount of fuel you just put in the car.

    You'll notice that the numbers you calculate are 5-10 mpg, at worst, lower than what the car is telling you.

    Lastly, how you drive matters. If you have a lead foot, you will not be able to get really good fuel economy out of the car. If you hypermile, you can get some really great numbers.
     
    #5 CooCooCaChoo, May 23, 2022
    Last edited: May 23, 2022
  6. RickyD

    RickyD New Member

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    Professor, thank you for the education. I am new to these cars coming from serious sports cars over the years.

    Bisco, I don't know the extent of damages to both cars. I do have a Toyota and state inspection certificate the cars meet specs. Tire pressures were set by Toyota dealership. I have a pro scanner that reads and runs tests in realtime the individual packs. Both cars are within specs. I will try Dr. Prius. Thanks.
    Your question:
    "how are you figuring miles per tank?"
    Both cars I fill up, reset trip, drive close to empty.
    Average mpg shown is 46 or 47 on the 2. Total tank miles 280. No manual calculation done. Just going by dash display.

    Coocoo, thank you for the battery explanation. The 2s SOC varies from 63 to 70% with my scanner.
    max EV block voltage is 15.39. min is 15.27.
    I will do your suggestion as it is sound and logical to do. Thanks again. My driving is mostly city about 6 - 10 miles daily. Weekends can vary from 20 - 80.

    All of the responses so far has been insightful, helpful, and reassuring to a new owner of a Prius.

    This a great welcome to the forum.
     
  7. bisco

    bisco cookie crumbler

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    yeah, there's just something completely wrong with 280 miles, have you considered the math?

    how many gallons went back in?
     
  8. RickyD

    RickyD New Member

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    bisco,
    Going to do the math after the current fill up.
    So far, half a tank shows 162 miles driven on the dash, 46 mpg. Only once since fill up been on the highway. My 3 tech will do 320 at half.

    Both cars are always on eco mode.
    I don't run ac as I like natural air.

    Sorry for long posts but I want to be as informative as possible for the great help you are providing.
    I really like these cars.
     
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  9. bisco

    bisco cookie crumbler

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    maybe the gauge is off. i think the key will be how many gallons you put back in each.
     
  10. dacoobob

    dacoobob Member

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    To really know what's going on, you need to be looking at the number on the gas pump to see how many gallons you're actually putting in your tank. The dashboard fuel gauge isn't a reliable indicator of how much fuel you actually have left-- especially if it's showing "empty" when you've only used 6 gallons of your 11-gallon tank.
     
  11. RickyD

    RickyD New Member

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    dacoobob,
    I will post my findings after I go through the current tank. Since I alternate between both cars, should take about 4 - 5 days.
     
  12. RickyD

    RickyD New Member

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    Ooookay.
    Went from full tank to empty (that was fun),
    Odo showed 293.6 miles driven to empty. Filled up til pump stopped. Total gas in was 10.5 gallons. So that is what my TWO is doing.

    Conversely, my THREE got 582 on a tank
    Both driven city only, no highway trips this week.
    Clearly the ICE is working more on the 2 than the 3. Dr Prius is next to try as my pro scanner shows the 2's batteries are within specs. Maybe amperage is weak?

    Again, both cars are 2016, the 2 with 151,300 miles, the 3 touring with 51,465.
     
  13. bisco

    bisco cookie crumbler

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    so the two has gone from 46mpg to 28mpg?
     
  14. RickyD

    RickyD New Member

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    bisco,rship
    Yeah, seems that way. Something is screwy.
    Today, drove 75 miles straight, no highway, just back roads and gas gage did not move from full.
    Battery indicator registered 80 to 100% most of the trip. Average mpg 49.1. Temp where I live has been 83 to 95 degees. Today 95.

    Since the car was salvaged (door damage), maybe something else went wrong. The ICE starts and stops alot compared to the 3.
     
    #14 RickyD, Jun 2, 2022
    Last edited: Jun 2, 2022
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  15. bisco

    bisco cookie crumbler

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    it does seem odd that the battery wouldn't get used more in that kind of driving.

    try the same thing with the 3 and see if the battery goes down more. are you driving gently or accelerating quickly?
     
  16. RickyD

    RickyD New Member

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    bisco,
    For testing, I've been driving gently, no ac, no highway driving, just rural roads between cities.

    I have a toyota dealership appointment today that has a prius factory tech on site all week who will check things out. We shall see...

    The 3 has been pretty solid on specs. History discovered is, new traction battery, and full calibration to specs. No such info on the 2.
     
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  17. dacoobob

    dacoobob Member

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    28 mpg! Wow, something is very wrong with that Two. Could be a million things-- a dragging brake, clogged fuel injectors, a bad sensor somewhere, battery issues, digital controller issues...

    Hope the Toyota techs can figure it out.
     
  18. bisco

    bisco cookie crumbler

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    .
     
  19. bisco

    bisco cookie crumbler

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    2016 3 with 51,000 miles has a new hybrid battery?
     
  20. CooCooCaChoo

    CooCooCaChoo Senior Member

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    What is the exact model of tires of the Bridgestones on the Two?

    Have you considered doing the routine maintenance on the Two? Spark plugs, air filter, MAF/throttle body cleaning. Running a fuel additive to clean injectors and valves? Varnish and carbon deposits can affect fuel economy.

    The only other thing I can suggest is that the NiMH battery on the Two is dying.