light knock, silent fan, great mpg

Discussion in 'Gen 2 Prius Technical Discussion' started by Georgios, Jul 11, 2018.

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  1. Georgios

    Georgios Junior Member

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    2008 Prius
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    I have decided to write about my small isuues of the greatest car on earth. I bought the 08 Prius with 140k+ miles and for 6 months I have done 15k miles. Bough Chilton manual at the beginning, changed the spark plugs with 4 OEM ones, PCV preventative change with toyota one and a at the beginning of ownership replaced both water pumps and belt.
    Did 5k miles oil changes with Mobil 1 and Original Toyota filter - This is a SUPERB and fun job to do on this car. Also drained the old trans oil and replaced with WS Toyota oil - again cheap and great job. Coolant too.
    Car runs like champ. Battery has power and drain pretty slow, still original one I believe
    And I purchased ScanGauge 2 From advanced auto with coupon for total of $130~
    I love that car. And do UBER with it.

    Adviced from @ericbecky ( big credits for that) I bought a Techstream and I have tested multiple stuff around the car, including the battery fan. It went thru all the speeds (did few times per week) and on top of that i though it might have some dirt but it was super clean fan and tube when I checked.
    PROBLEM 1 - BATTERY FAN
    That being said - I have only heard it once running on low speed. I live in Chicago and it may be cold in the winter but recently 95+F and running 150 miles a day traffic and highway - this fan is missing when driving. Maybe I do not hear it..I dont know! Back in 2013 drove newISH 2007 Prius 2 with way lower miles on around 100F and that battery fan was like a helicopter from Korean war.
    Is this normal or could it be a problem?

    PROBLEM 2 - KNOCKING
    I know in the manual says to put gas 91octane or more but since few other guys run on 87 with no issues I decided to put 87 and try. After the 3rd tank with 87 I realised i hear knock on light to moderate load 2000RPM and up and got really scared for the car and went back to 93 since I cant find 91.
    Is there other people out there that has problem with 87 or 89 octane gas?

    And by the way I decided to do full-to-full gas tank test and see if the trip computer shows correct and amazingly it does I had around 1 gallon gas left I believe although the scangauge2 shows every 2.5% . The pictures are from the test with the 87 octane while doing UBER in Chicago, so car has 1-2-3 passengers at much of the time. - 53 MPG. WOW. What a car

    EDIT: I forgot to mentioned I have 195/65/15 installed which are for sure ruining somewhat the gas mileage but the car seems more comfortable and stable in windy days :D
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    #1 Georgios, Jul 11, 2018
    Last edited: Jul 11, 2018
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  2. dolj

    dolj Senior Member

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    This is good, you should not hear it. You have no problems.
    No, this is not normal and is likely indicative of looming HV battery problems.
    I have used the equivalent of 87 AKI and while it generally is not harmful (the car retunes itself down) there is a tendency to light knocking under load. I also noticed lower power and got fewer miles per tank. I now only use the equivalent to 91 AKI and notice none of the problems I mention with using 87 AKI. I get on average 120 more miles per tank and with the prices here, it is cheaper, per mile, to use 91 AKI, even though 91 AKI is more per gallon than 87 AKI.

    Using 93 AKI will not do any harm, but is just an extra drain on your wallet for no benefit, assuming that 93 AKI is more expensive than 91 AKI. If this is the case, seek out a gas station that has 91 AKI.
    195/60/15 is standard fitment here and I have no problem achieving year on year average of 50 MPG (US), so I don't think the size is the issue, if you have in fact noticed a lower MPG since changing to the wider tire. There will be some other issue that is a factor in a lower MPG.
     
    #2 dolj, Jul 11, 2018
    Last edited: Jul 11, 2018
  3. ITBland

    ITBland Active Member

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    In the US, the octane number posted on the pump is usually (R+M)/2 or the Anti-Knock Index number. The R is the Research octane and to get 87 AKI, it would normally be 91 Research octane, which is what is specified by Toyota. To quote the Owner's manual:
    Something is wrong, try a different brand of gas, or a different gas station on 87. If you still have knock, get it checked out!
    Edit: Look at pg 472 of your 2008 Prius Owner's Manual, there is a list of additives that are bad for your Prius. I don't know what BP is using in your area (Gas is formulated differently, in different regions), but it might be worth looking into it or changing brands.
     
    #3 ITBland, Jul 11, 2018
    Last edited: Jul 11, 2018
  4. ITBland

    ITBland Active Member

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  5. dolj

    dolj Senior Member

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    Some engines, as they age, do not perform with 87 AKI. Yes, something is not right, but the simple fix is to use 91 AKI.
     
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  6. Georgios

    Georgios Junior Member

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    I just looked at the manual again and looks like i missed to notice that 91 is the RON (I though it was RM/2), so yeas... 87 AKI in the US.
    Probably this gas station had a bad gas or something. After I put the 93 the knock went away permanently.
    In Chicago I cannot find 91 but 97 89 and 93 are everywhere. I am thinking to put half - half with 93 and 87 gas which is going to equal it to around 90. I will try just 87 again later on from Shell for example as that knocking was the gas from the BP, so it is very possible that from thousand of gas stations, some times the gas itself or the gas pump mixer does a bad job.

    Actually 195/60/15 maybe wider than the standart 185/65.15 but is tiny bit shorter so its not a surprise better mpg and accelaration.

    the old tires 185/65/15 I drove for like 2 days and could not really collect MPG data. Just overall handling was as usual. Actually even if you use the same exact tire size and brand, when install new tires a car always has better handling and comfort over old flat plastic tire. Car transforms itself

    I believe the 195/65/15 takes the MPG down over the 185/65/15 and not improve it. It is maybe half, maybe 1 or maybe 2 MPG but the 195/65/15 is bigger and wider and also more heavier. In tirerack they have specs and weight of a tire. Its like 18lbs vs 19 or 20 lbs for the bigger tire. Also the car sits a bit higher which also ruins the perfect aerodynamics. Overal 1 or 2 mpg arent that much, You can easily make that difference up with carefull driving so as long as I can be happy with the setup everything is OK


    In the future if I find cheap Touring wheels I will install them. That being said - does anyone know the exact weight of a touring wheel vs the regular wheel?
     
  7. dolj

    dolj Senior Member

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    It only appears to take the MPG down due to it ending up having a larger circumference. The larger circumference means the distance is under recorded so the car thinks it has travelled less than it has in reality. The correct tire size in 195 is 195/60/15 (or 195/55/16 for the touring wheels).

    Also, the extra weight in the touring 16" wheels makes them less economical.
     
  8. Georgios

    Georgios Junior Member

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    yes, i forgot that some distance isnt measured. The difference is 2% which on 533 miles is 10.66 miles, thats probably around 1 mpg more than what it shows.

    Also i got the tire light on, and techstream shows it is ID3. I found out ID3 is Rear left tire.
    They should have named them in the techstream but i did try 1 by 1
    ID1 - FL tire
    ID2 - FR tire
    ID3 - RL tire
    ID4 - RR tire
     
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