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Avg. MPG gave DROPPED!!!

Discussion in 'Gen 2 Prius Fuel Economy' started by jbean, Jul 13, 2016.

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  1. jbean

    jbean Junior Member

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    I've been using Top Tier gas: Costco and recently 76.

    Since I don't know if I have dirty injectors, is it safe to use something like Sea Foam?
     
    #21 jbean, Aug 11, 2016
  2. jbean

    jbean Junior Member

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    The MPG are now slowly dropping. I'm in the 27s. When I started this thread it was in the high 29s (after ALWAYS running in the low 40s in town). I'm NOT a DIY car maintence person, so I rely on the dealer and you folks. The dealer is worthless. I'm leaving on a trip on Sunday and feeling nervous about unreliable gas consumption. Is it safe to use a gas cleaner and what product is recommended to buy? What if I don't have dirty fuel injectors (might be calling it by the wrong thing)? Will it mess things up?

    I read here somewhere that short trips cause more buildup of something in the gas tank? True?
     
    #22 jbean, Aug 11, 2016
  3. bisco

    bisco cookie crumbler

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    how many miles on her?
     
    #23 bisco, Aug 11, 2016
  4. jbean

    jbean Junior Member

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    Approximately 40,000; very low.
     
    #24 jbean, Aug 11, 2016
  5. fuzzy1

    fuzzy1 Senior Member

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    #25 fuzzy1, Aug 11, 2016
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  6. bisco

    bisco cookie crumbler

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    wow! that's amazing. you can check your 12v under the hood with a simple digital volt meter. if you're interested, let me know.
     
    #26 bisco, Aug 11, 2016
  7. jbean

    jbean Junior Member

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    I've been reading the posts you recommended. Thank you.
    1. I keep the tire pressure up to par/~2 weeks ago it was checked at the dealer. I can tell when my tire pressure starts to get even slightly low.

    2. Would you like me to answer the questionnaire in the thread it's in, or here?

    3. In the DO-IT-YOURSELF TEST PROCEDURE (thanks to jdenenberg): do I need a voltmeter to do it, or just follow the steps? I can do anything software related but not anything in the engine.
     
    #27 jbean, Aug 11, 2016
  8. bisco

    bisco cookie crumbler

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    just follow the steps.
     
    #28 bisco, Aug 11, 2016
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  9. jbean

    jbean Junior Member

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    I'm happy to check this myself, but isn't this something the dealer should be checking? The service manager told me his "hands were tied" since there are no alert messages showing on the dash. I don't get it. They should pay me. lol.
     
    #29 jbean, Aug 11, 2016
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  10. fuzzy1

    fuzzy1 Senior Member

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    'Up to par' and 'checked at the dealer' are not the answers we are looking for. We want you to check it yourself, and report back to us with actual PSI numbers, preferably when still cold in the morning. If you want great MPG, this is one of those things that must not be left to the newest and lowest paid employees at the dealership. They don't have any skin in the game, and won't look beyond trouble codes (Check Engine Light) and clearly broken parts.
    Here. That thread is locked, you cannot post there.
    On a Gen2, you can do it by stepping through the dashboard menus. No voltmeter is required. On later models, a voltmeter is needed.
    We already have too much experience with them testing and reporting that the battery is good, when it really isn't. Plus, the symptoms of dying 12V batteries in Prii are completely different than in traditional non-hybrids.
     
    #30 fuzzy1, Aug 11, 2016
    Last edited: Aug 11, 2016
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  11. bisco

    bisco cookie crumbler

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    most dealers will happily take your money to check the 12v. you can try an auto parts store.
     
    #31 bisco, Aug 11, 2016
  12. jbean

    jbean Junior Member

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    My car hasn't been driven in 24 hours and is parked in my garage. It's 96 degrees outside right now, and it's about 86 in the garage. Is that cold enough?
     
    #32 jbean, Aug 11, 2016
  13. bisco

    bisco cookie crumbler

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    yep.
     
    #33 bisco, Aug 11, 2016
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  14. fuzzy1

    fuzzy1 Senior Member

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    The main point is that it isn't road-warmed, so that is fine. But we should make a separate allowance for your normal morning temperatures compared to now.
     
    #34 fuzzy1, Aug 11, 2016
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  15. jdonalds

    jdonalds Active Member

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    I was using a Bluetooth adapter for the ODBII connector coupled with the Torque app on my Samsung Galaxy phone. I was monitoring cell resistance and cell voltage (as I remember, it was a year ago). The car had about 150K miles at the time. I could see no indications that any one cell was different than the others. Up until that time I had assumed there was something wrong with the battery or electric drive system in general. Then I began to notice how difficult it was for me to achieve over 50 mpg instantaneous readings when the ICE was in use so I shifted my focus to the ICE.

    Previously I had a Suzuki motorcycle that was less than a year old with only 2.000 miles on it. It began to run rough the very night that I listed it for sale on Craigslist. Changing the spark plug was not easy on that DR-Z400S so I decided to give a fuel additive a try. Seafoam had great reviews on amazon. I drove the motorcycle to Napa Auto Parts, picked up a can of Seafoam and dumped half of it in the gas tank. Before I had driven a mile the engine was running as smooth as ever (well for a thumper that is).

    When I wanted to try something in the Prius I naturally returned to the Seafoam that had worked in the motorcycle, and again it worked. I presume I had dirty injectors. Ever since then, about 12,000 miles further on, the Prius has behaved like new.
     
    #35 jdonalds, Aug 12, 2016
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  16. jbean

    jbean Junior Member

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    - What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations)
    27.8 mpg from the trip computer.

    - What fuel economy are you expecting and why?
    41.0 because that's what I've been getting since October 2008.

    - What are the approximate outside air temps?
    100+ most days, or high 90s.

    - How long are your trips?
    Short

    - 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?
    I've been driving in the city only since April 2016. Average speed is ~30 - 40 mph. Some stop and go.

    - What region/state are you in? (if you haven't set your location in your profile)
    Central California.

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

    - Is your oil overfilled? (i.e. above the full mark on the dipstick)
    I haven't checked.

    How old is your 12v battery?
    ~ 8 years.

    What is the voltage reading of your 12v battery after sitting over night? (Method Here)
    11.9 Volts

    Have you had your alignment checked? Any pulling or abnormal tire wear?
    Alignment was done in January 2016, when new tires were installed.

    - 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).
    Continental TrueContact
    185/65R15 86H

    - What are your tire pressures?
    34 psi in each tire.

    - 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.)
    2001 Lexus IS 250
    Manual transmission
    I don't remember the mileage

    - How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking?
    I don't understand the question.
    I'm not heavy on the brakes.

    - Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on?
    No

    - Are you driving using D or B mode?
    D

    - HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to?
    AC

    - If reporting a mileage drop, did anything significant change on your car (e.g. accident, hit a curb or big pothole throwing off alignment, oil change/other maintenance/repairs, changed tires or wheels, etc.) or your commute?
    I changed tires in January 2016. The mileage dropped 2-3 months later.
     
    #36 jbean, Aug 12, 2016
  17. fuzzy1

    fuzzy1 Senior Member

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    The change to only short trips in April is the glaring issue that pops out at me. You don't give an actual distance, but short trips don't allow the fuel cost of engine warm-up to be spread out over very many miles, so the result is low trip MPG. 100+ temperatures do the same with the fuel cost of the AC's initial cabin cool-down.

    You didn't give your AC settings. 'Lo' temperature setting and high fan speed will eat more fuel than a 75F setpoint and lower fan speed. Pointing all the dash vents at the driver's face, and closing the right-most passenger vent, will make warmer/slower setting more tolerable. But with your outside temperatures, AC is not an option, it is a necessity. You may just have to write this portion off as a cost of living in a hot place.

    The front tire pressure is also low, it should be at least 35. If morning temperatures are significantly lower than the 86F when you measured it, then those tires may be another 1 or 2 psi lower still. Many of us boost MPG slightly by setting the pressures significantly higher, 40-44, but that is a matter of personal preference. It increases ride harshness, not everyone can accept this.

    The 12V battery is old (pretty much end of life), and voltage low, but I can't say it is low enough to be an actual problem. The blatant cases of aging batteries contributing to low MPG had lower voltages than that. Yours might merely be a case of short trips not allowing enough recharge time, which could be (temporarily) cured by putting it on a recharger (slowest rate) overnight. While some folks have seen an immediate improvement from replacing this old battery, others did not.


    That is my take so far. I haven't looked up the tires specs for LRR rating.

    What do other folks see in this?
     
    #37 fuzzy1, Aug 12, 2016
  18. bisco

    bisco cookie crumbler

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    agreed, start with the 12 volt battery, tyres pressure and move on. short trips are a killer, nothing you can do, but it would be worthwhile taking a 20 mile trip to see what shows up for mpg. that would be a better comparison to your 41.
     
    #38 bisco, Aug 12, 2016
  19. jbean

    jbean Junior Member

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    Thanks for your response. I wasn't 100% clear about my driving habits. From 2008 - ~2012 I used to drive a combination of city driving (I live in the same place) and every few months I'd drive 500 miles round trip. When I changed my driving habits, the MPG did not go lower. For several months recently I've been driving less than 10 miles at a time. On Sunday I'm driving out of town, approximately 1 hr. each way. I need to fill up the tank and I'm not sure what kind of gas to buy. I don't know if it makes a difference? I've been buying Costco's gas exclusively since 2008, then the Toyota service manager told me to quit buying Costco's gas until the weather cools in October. So I put in 3/4 of 76 gas. I don't know if gas is a factor in this equation.

    When I use the a/c typically I run it on the medium level, occasionally on HIGH to start off, and usually run it at about 74-75 degrees.

    The average low temperatures here yright now average 66F.

    I'm willing to increase the tire pressure. Since I rely on the dealer for help, just to drive there, it's about a 10-15 minute drive. To achieve a 40 psi, they would put in 42? to accommodate for the warmed up tires?

    What is the average cost of a 12 volt battery? When I talked with the service manager he said he couldn't do anything to my car since there are no warning lights. He said his hands are tied. Is this true? There is no one where I live who works on Prii except the dealer. One hour away I might be able to find an independent mechanic. What is a recharger, where would I get one, and is this something a non-car person could handle? What do they run?

    When I go out of town on Sunday, will a one hour drive on the freeway, going about 75mph, should I see a difference? And if not, then what? I hope I have answered all your questions. I want to get to the bottom of this. Thanks.
     
    #39 jbean, Aug 12, 2016
  20. bisco

    bisco cookie crumbler

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    you can get a battery for $150. to $200. plus labor. type of gasoline makes no mpg difference. you do not need a prius mechanic for many of these services.
     
    #40 bisco, Aug 12, 2016
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