Unusual Gas Mileage

Discussion in 'Gen 2 Prius Fuel Economy' started by jazz-n-prius, Jul 27, 2021.

  1. jazz-n-prius

    jazz-n-prius New Member

    Joined:
    Jun 2, 2021
    21
    2
    0
    Location:
    So Cal
    Vehicle:
    2008 Prius
    Model:
    N/A
    So I have only been able to do a fill ups and these are my results.

    Tank 1: Almost all city mileage: 37 mpg calculated (38 Computer MPG). I drove very easy on the gas and light on the brakes.

    Tank 2: Almost all highway mileage: 46.8 mpg calculated (48.7 Computer MPG). I was driving faster between 75-85 mph for the majority.

    Tank 2 is about what I would hope for. I am sure if I was going 65-70 I would have maybe hit the 50 mpg mark.

    What I am wondering about is Tank 1. When I bought it I thought I would be about 10 mpg higher in the city than what I achieved. Here are the specs that I have for my Prius.

    -51k original miles
    -original battery (seems to be functioning well)
    -AC is always on (live in inland Souther California where it is always 95-110 every day since owning it)
    -Goodyear Assurance All Season (I do not believe they are the Fuel Max-but I would expect that to affect my highway milage more than city milage.)
    -the previous 1 owner always had it serviced at the Toyota Dealership every 6 months (even though it only accrued 1500 miles or so-I have documentation showing each service).

    I have seen on the forum that some people recommend getting a tune up, but at only 51k I would not expect it to need it. Any other ideas. I am assuming that using the AC is hurting my mileage, but it is hard to believe that it would hurt it by about 10 mpg compared to what many of you are achieving in city driving.
     
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    93,829
    42,527
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    1) the tank has a bladder which does not allow even filling every time.

    2) you don't need a tune up.
    if anything, you should recondition the battery.
    the only thing that prius don't like is not being driven.
    batteries degrade from sitting.
    the battery would affect city driving much more than highway due to the stop and go nature and regeneration vs cruising on mostly engine.
    a weaker battery will not be able to absorb as much energy regenerated, nor produce as much as a newer one.
     
  3. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    5,461
    2,188
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    Your results look "normal" to me.
    Steady state driving will almost always yield a higher average MPG number than stop-and-go situations.......up to a point.

    This is partly because the stop and go usually involves shorter trips.
    Longer trips averages out the startup penalty more.
     
  4. jazz-n-prius

    jazz-n-prius New Member

    Joined:
    Jun 2, 2021
    21
    2
    0
    Location:
    So Cal
    Vehicle:
    2008 Prius
    Model:
    N/A
    @sam spade 2 I was under the impression that most people are getting higher MPG in the city than the highway (like how the EPA rating is higher for city than highway).

    As @bisco said, maybe I need my battery reconditioned. I do agree that it makes sense that if the battery health will affect the mileage more for city than highway. Does anyone have any companies that they recommend in the Southern California area. I have heard that some do it well, and others do not.
     
  5. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    93,829
    42,527
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    i haven't. most here buy the prolong reconditioner for less than a private company charges, and do it themselves.
    use caution, there are a lot of scammers out there.
     
    srellim234 likes this.
  6. jazz-n-prius

    jazz-n-prius New Member

    Joined:
    Jun 2, 2021
    21
    2
    0
    Location:
    So Cal
    Vehicle:
    2008 Prius
    Model:
    N/A
    @bisco what prolong reconditioner do you recommend? I have never heard of buying one yourself.
     
  7. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    5,461
    2,188
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    There is a difference between "city" driving, that is driving at a steady but slow speed, and "stop an go" driving.
    With most vehicles, you get the best mileage at a STEADY speed of 40-50 MPH.
    It goes down from there with a lot of stops or much higher speed.

    Maybe you do NOT need to be messing with your battery.
    "reconditioning" is mostly a myth. The gain is small and short lived unless maybe you start early and do it fairly often.
    Taking one shot at it is a total waste of time and money.

    P.S. Bisco has NINETY THREE THOUSAND posts on here. Have you read many of them ?
     
  8. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    93,829
    42,527
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    prolong-battery-charger
     
  9. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    93,829
    42,527
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    ignore the priuschatter on priuschatter hate above, and do your own due diligence;)

    you can test the battery health with dr. prius app
     
  10. mmmodem

    mmmodem Senior Taste Tester

    Joined:
    Nov 17, 2011
    2,664
    1,640
    0
    Location:
    Bay Area, CA
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    I get lower mpg in the city than on the highway. Upper 30's vs mid 40's for city vs highway seems about right for my Gen2. There's probably dozens of reasons why this is contrary to the EPA. If there is stop and go traffic on the highway during my commute, I get better fuel economy. I can only guess that the EPA city tests mimic my stop and go highway traffic driving style but not necessarily my city driving.

    Anyway, I would be worried if I averaged 37 mpg in my Prius. Since you got 47 on the next tank, you're matching what I get for mostly highway driving. 10 mpg is a huge difference but with one data point, it could just be a fluke.
     
    srellim234 likes this.
  11. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    15,124
    8,447
    90
    Location:
    Western Washington
    Vehicle:
    2012 Prius
    Model:
    Three
    The EPA (and CAFE) City test cycle is most definitely "stop and go", not steady speed. Here is the official speed vs time profile:
    upload_2021-7-28_20-15-17.png

    With a Prius, you get the best possible MPG at a steady speed of 15 to 20 mph, and can exceed 100 MPG this way. While this is very impractical in common U.S. use, some Japanese commuters were able to push this to get some incredible three-digit MPGs and four-digit single-tank distances.
    Don't put much stock on that EPA twist of having a higher city than highway score. It is mostly just an artifact of the artificial fudge factors contained in the EPA scoring system, used to discount the high MPGs achieved by expert drivers running special speed profiles on stationary dynamometers, down to the more typical numbers experienced by ordinary drivers in real world conditions. The EPA's equations have quite different city and highway fudge factors.

    Almost nobody has an actual driving profile that matches the official EPA - CAFE cycles. Some Prius drivers do get better in city driving, while many others do better in highway conditions. Because the EPA scoring system contains artificial elements, and most likely doesn't match your driving patterns, don't worry about which of those groups you are in. Don't overthink it.
     
  12. Another

    Another Member

    Joined:
    Jun 22, 2021
    255
    55
    0
    Location:
    Naples, Florida
    Vehicle:
    2007 Prius
    Model:
    Touring
    were both tanks filled at the same station? Were they either one off brand gasoline? Could it have been an e-85 crap refill either by your mistake or because the tanker misfiled it? Much of the summer gasoline is crap especially in places like California. The oxygenates that refiners put in antismog blends to meet emission standards to help combustion, minimize NOx pollution are very poor energy to volume fuels. I’d try more tests with different brands before more involved analysis. That being said it takes a bit of relearning to drive a hybrid for max mpg especially in city driving.
     
  13. jazz-n-prius

    jazz-n-prius New Member

    Joined:
    Jun 2, 2021
    21
    2
    0
    Location:
    So Cal
    Vehicle:
    2008 Prius
    Model:
    N/A
    @Another Both were filled at the same station a few days apart. Each one I did check to make sure it was full by topping off. I have owned hybrids before. I had a 2019 Rav4 hybrid which was amazing. I was always able to get the EPA rating in the city and exceed it on the highway, so I do have experience driving a hybrid and understanding how to maximize the mileage.
     
  14. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    5,461
    2,188
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    THAT is not a good thing to do.
    It can plug up the evap emission loop and cause the engine to run bad.
    MY owners manual specifically says to NOT do that.
     
  15. Another

    Another Member

    Joined:
    Jun 22, 2021
    255
    55
    0
    Location:
    Naples, Florida
    Vehicle:
    2007 Prius
    Model:
    Touring
    Same station a few days apart can be a bad batch of gasoline or a misfiled tank. I’d try more tests over the next few weeks with different brands before more involved analysis.
     
Loading...