2008 Prius not getting good gas mileage.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Kenneth Maloney, Aug 11, 2020.

  1. Kenneth Maloney

    Kenneth Maloney New Member

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    So I'm a new Prius owner and have never owned a hybrid before. I have some questions.

    First, it charges the battery just fine when traveling lower than 60 mph. But as soon as we take her on the highway it drains the hybrid battery down to nothing and revs higher than it sounds like it should. I'm wondering if this is normal operations, or if this is abnormal and maybe the hybrid battery is going out.

    Second, is less than 30 mpg mostly surface streets a normal condition as well? We barely got to drive 280 ish miles on a full tank and it's already one gas node to empty. What can I do to check and maybe fix this condition?
     
  2. JC91006

    JC91006 Senior Member

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    From what you're describing, I'm assuming your engine has over 200k miles and is quite worn, combine that with a weak HV battery (with possibly your AC blasting) and you end up with what you're describing.

    I once owned a 2006 with an engine that didn't get many oil changes. The power produced by the engine is much lower than the other Prius cars I've owned. As it aged and got older, I experienced everything you are describing
     
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  3. SFO

    SFO Senior Member

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    Welcome to PriusChat!!

    Likely that you are (or the HV battery is) on borrow time, how many miles are on the vehicle?

    You still have options, and best to plan accordingly (balance, rebuild or replace) before you are stuck in a inconvenient or costly situation.

    The other option would be to ignore the impeding doom (or learning experience), while taking things a little slower and enjoying the ride.

    You can measure the fuel consumption more accurately by dividing the number of miles driven by number of gallons pumped at the station.

    Have you checked for dealer maintenance (or shenanigans) by running the VIN at : Welcome to Toyota Owners
     
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  4. Kenneth Maloney

    Kenneth Maloney New Member

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    It's gotta about 200 K on her. And the mpg estimate I gave you is based on that math. I changed the oil, and I'll be changing the spark plugs tomorrow. It's just odd that the hv battery is drained while going on the freeway and it won't charge at all while going at freeway speeds. I figure the battery will need to be replaced, and am planning on doing so myself because I know that it hasn't been changed in 12 years.

    As for the shenanigans, that's good advice. Thanks.
     
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  5. edthefox5

    edthefox5 Senior Member

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    How many miles on it Kenneth. 225,000?

    You need a new hybrid battery and like JC said the motor probably eat's oil like crazy. First thing in the morning check the oil dipstick
    its probably out of oil.

    We see see so many of these.
     
  6. TMR-JWAP

    TMR-JWAP Senior Member

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    No, initial gut reaction, based only on your stated symptoms, is this is not normal at all. The battery should provide very little assistance while on the highway and should essentially be float charging/discharging when at steady highway speed, maintaining mid-high blue bars on the mfd screen. The battery WILL discharge as mentioned if there is limited power from the engine, or something else is causing significant drag on the car that the engine can't handle.

    Is there a check engine light? or a large red triangle? Any warning lights on the dash at all? If so, could you provide a readout of the codes?

    Normal operation at low speeds and abnormal operation at high speeds could be indicative of something as simple as a clogged exhaust system, intake system, or limited flow in the fuel system.
     
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  7. Kenneth Maloney

    Kenneth Maloney New Member

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    So when I initially bought it, it was over a quart low. I changed it last week but saw little improvement. I'm certain the battery needs to be changed and I plan on doing so once I can convince my wife to get a new one. It's not as hard as you would think to do so, as long as you follow the steps carefully it can be done with only hours and about 1500 spent.

    Yeah. Even when we're at a steady speed, the battery doesn't charge at all. There's no codes currently nor is there a red triangle. Is there a place that would test the hybrid battery that won't cost an arm or a leg? The exhaust system is a great idea, so thank you for that, I'll run a CAT cleaner through it and look at possibly replacing it.
     
    #7 Kenneth Maloney, Aug 12, 2020
    Last edited by a moderator: Aug 12, 2020
  8. bisco

    bisco cookie crumbler

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    you can't trust the bladder in the gas tank, how many gallons to refill?
     
  9. SFO

    SFO Senior Member

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    The gold standard for retrieving OBD2 codes would be a 'mini-vci' cable and a copy of techstream, which is the same software the dealership technicians use for repairs. Others get by with using an OBD2 bluetooth adapter with an app like Dr Prius or Torque.

    If you're buying a bluetooth adapter, read up on quality/compatible products : Hybrid battery diagnostic and repair tool for Toyota and Lexus

    Dr Prius can do a 'one click'(?) guesstimation of the HV battery health, or with a little more effort you could use Techstream or Torque as well.
     
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  10. jerrymildred

    jerrymildred Senior Member

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    +1 to what @TMR-JWAP and @JC91006 suggested. The hybrid battery may or may not be weak, but it's pretty clear that the engine is not producing normal power. Being over a quart low when they sold it is not a good sign at all. But there may be plenty of other things bogging it down. It might need a compression test. If that's good, then a thorough tune up.
     
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  11. edthefox5

    edthefox5 Senior Member

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    TMR is right here.

    If you have no codes its not the hybrid battery. If that fails or the inverter pump fails and overheats the inverter it throws lots of codes and always the fatal RTOD red triangle of death. Whatever it is is out of monitoring range or scope.

    So you may just have a a very clogged cat which is caused by excessive oil blow by from a completely worn out motor. We see this often no one checks there oil anymore the car starts to eat oil the oil change place never checks the oil level when you roll in owner never checks the oil so owner has no idea its eating oil till one day the check engine light comes on as the oil sump is dry. A real good one of those or more than one will kill the piston rings allowing lots of uncombusted crap into the cat.

    I check the oil every saturday on my cars. Have for years and years. Always must be at the full line. I blew up a car I loved and dearly needed running it dry when i was seventeen. Learned my lesson good. Your car is the most important thing in your life when its not there.

    Seen a bunch of those here the clogged cats on this site and in this case is just the symptom of the bigger problem the blown engine.

    A compression check of the cylinders will confirm this hypothesis.Toughest little engine in the world but must have every drop of its 3.6 quarts of oil.
     
    #11 edthefox5, Aug 12, 2020
    Last edited: Aug 12, 2020
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  12. JC91006

    JC91006 Senior Member

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    I would recommend against the $1500 HV battery, it's the engine that's the problem here. If you're willing to invest in a new engine, then you can replace the $1500 HV battery. If not, I would just sell the car and get something better
     
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  13. GrayRaceCat

    GrayRaceCat Junior Member

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    Hi Kenneth, Any update on the 2008? I am curious what you found out.
     
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