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P420, Low MPG, Burning Oil

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Rafikiro, Dec 10, 2017.

  1. Rafikiro

    Rafikiro Mockba

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    Hi all. I have a 2008 Prius with package 2 I purchased new with 4 miles on her. I want to keep her around for a while yet if possible but am having issues with an intermittent P420 code, low mpg, and burning about a quart of oil every 1,000 to 1,500 miles. She has 231,548 miles. Just did an oil change last night and replaced underside skids. She had a run in with a deer just about a year ago and I had to replace both water pumps as a result but otherwise just looks ugly because I have not found matching fender and hood so the fender is the wrong color and hood has the deer body impact dent still.

    The P420 is intermittent and seems to come on when the oil is low or gas is very low, and goes away when these are fixed. I am still working on remembering to check the oil every gas stop (which is like every other day now that the gas bladder basically holds 6-7 gallons). So the issue may lay in the oil burning. Thoughts on where to start to diagnose? Spark plugs where changed with iridium tip maybe 10k miles ago, there were wrong spark plugs for about 15k miles just not iridium tipped. Cylinder 4 plug seems to be burned more on last two replacements. MPG is down in the 30's for the last year or two. Car is almost all highway and lifetime average MPG is just below 44 with 97.5% of fuel information obtained to get that number.
     
    #1 Rafikiro, Dec 10, 2017
  2. bisco

    bisco cookie crumbler

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    you're still way above toyota's spec. you may need an engine overhaul, why not just keep an eye on the level and keep it topped up?
     
    #2 bisco, Dec 10, 2017
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  3. Rafikiro

    Rafikiro Mockba

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    Thank you for the reply. Thats what I have been doing but would like to see if there is anything that can be done without costing a ton to get her back in better shape. I am fairly handy so anything I can do myself I would like to do. Any reasoning why the low oil and gas is causing the P420 code?
     
    #3 Rafikiro, Dec 10, 2017
  4. Raytheeagle

    Raytheeagle Senior Member

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    How long have you been topping up every 1000-1500 miles? With the amount of oil sent through the cat, probably not surprising that you have a cat code.

    Do you have access to Techstream or software that can read the o2 sensors?

    Have you considered a replacement cat? Since you don’t have to worry about the CA regs, you can get a good aftermarket one and be good for awhile.

    Hope that helps(y).
     
    #4 Raytheeagle, Dec 10, 2017
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  5. Rafikiro

    Rafikiro Mockba

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    I dont currently have the tech to get the o2 sensor info, have a good reader but as far as I have been able to figure it does not read that but will check again. The oil has probably been say just more than a year, I noticed it a short while before hitting the deer. Main issue with just doing the cat is $800 quote from mechanic and I cant get under there to saw it off or weld a new one back on.
     
    #5 Rafikiro, Dec 10, 2017
  6. Raytheeagle

    Raytheeagle Senior Member

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    You can also try to clean the cat out with various methods.

    Look on you tube for some solutions.

    $800 is high for what is involved. Have you called someone else for comparison?
     
    #6 Raytheeagle, Dec 10, 2017
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  7. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Yeah, 1.1 quart every 600 miles. Really ballsy statement, grammatically correct is the best I can say.

    I wonder if the EPA or someone should cast an eye on this, or just consumer protection. "Acceptable" oil consumption is a stat that should need to be disclosed on the Monroney Sticker, my 2 cents.
     
    #7 Mendel Leisk, Dec 10, 2017
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  8. Rafikiro

    Rafikiro Mockba

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    You are saying I am at half what is acceptable in oil consumption? Geeze. I through a quart per oil change was horrid before this started.
     
    #8 Rafikiro, Dec 10, 2017
  9. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    What irks: Toyota has just dreamed up this number, deemed it "acceptable". I keep proposing: this "acceptable oil consumption" stat should be displayed prominently in sales brochures. Maybe @Prius Team can respond?
     
    #9 Mendel Leisk, Dec 10, 2017
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  10. m.wynn

    m.wynn Senior Member

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    Yeah, right...:cool:

    And to think Toyota didn't have a single model on that Consumer Reports list of the REAL oil burners. Wonder what those brands deem acceptable burn rate?:eek:...


    Your burn rate is actually quite typical of what we see from 1/4 million mile Prii around here. It's the odd high mileage Gen 2 that doesn't burn a fair amount of oil. Conventional oil and a 5k miles interval was a bad idea for these engines. Often an owner that reports little to no burning took it upon themselves to go full synthetic when the car was young. And P0420 is probably the most common engine ECU code reported, too. As Ray says, you're lucky you're not in Cali or New York where you pretty much have to pony for an OEM cat to pass state inspection. Assuming your hybrid battery is ok, the low mpg probably IS due to the oil choked cat. You should, however, be able to do an aftermarket like Walker or a weld-in Magnaflow for half of that quote, less if you do the work yourself. I'd leave your A/F and O2 sensors as is until they actually code. P0420 pretty much always points at the cat with the Gen 2 Prius, and you're burning enough oil that it basically assures it. Keep the oil topped and drive on. The car sounds great otherwise, the Gen 2's are tanks.
     
    #10 m.wynn, Dec 10, 2017
    Last edited: Dec 10, 2017
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  11. Rafikiro

    Rafikiro Mockba

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    Thanks! Good to hear this report m.wynn. Unfortunately on the synthetic oil I did that about half the time for the first five years depending on poverty level at the time of oil change, but I think I always did at least partial synthetic.... Been Synthetic all the way for at least 100,000 miles. My goal is to keep her as long as my previous 17 year old Sentra so at least seven more years, but the new safety tech has me somewhat with a wondering eye, though the tech upgrade from that 91 Sentra to the 08 Prius was pretty amazing at that time too!

    Of course that Sentra had a total of 173,000 miles at 17 years and I am over 50k past that already.
     
    #11 Rafikiro, Dec 10, 2017
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  12. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Interesting video on conventional vs synthetic oil:

     
    #12 Mendel Leisk, Dec 10, 2017
  13. Rafikiro

    Rafikiro Mockba

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    Looked into the self install on the cat, any thoughts on no weld cats? I could get that in myself! Also today the code came on, new oil still full, gas at half, normally it comes on when oil or gas is ultra low. Any thoughts on this? Any suggestions on driving style that may be adding enough to trip the sensor?
     
    #13 Rafikiro, Dec 11, 2017
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