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Re: Why does using higher octane fuel cause the check engine light on the prius?

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  • David Cranford
    I like it. Behiving obviously means the car is driving as sweet as honey. ... trying the re-boot (simply, re start the car), and if it feels like it s
    Message 1 of 10 , Dec 2, 2006
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      I like it. "Behiving" obviously means the car is driving as sweet as
      honey.

      --- In toyota-prius@yahoogroups.com, pmb <PriusPete@...> wrote:

      > In future, though you do want to find the real cause, avoid a tow by
      trying the re-boot (simply, re start the car), and if it 'feels' like
      it's behiving normally, just drive on.
      >
      > Pete
      >
    • Ed & Ruth Young
      David Cranford wrote: I like it. Behiving obviously means the car is driving as sweet as honey. Oh my gosh....our woner droup has yet another new word! Way
      Message 2 of 10 , Dec 2, 2006
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        David Cranford wrote: I like it. "Behiving" obviously means the car is
        driving as sweet as honey.


        Oh my gosh....our woner droup has yet another new word!
        Way to go Pete...... :-)

        --- In toyota-prius@yahoogroups.com, pmb <PriusPete@...> wrote:

        In future, though you do want to find the real cause, avoid a tow by
        trying the re-boot (simply, re start the car), and if it 'feels' like
        it's behiving normally, just drive on.
      • pmb
        yes - exactly! (caught that just _after_ I hit the send button, of course. another one for the woner lexicon...) Pete
        Message 3 of 10 , Dec 2, 2006
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          yes - exactly!

          (caught that just _after_ I hit the 'send' button, of course. another one for the woner lexicon...)

          Pete

          -----Original Message-----
          >From: David Cranford <dcranford@...>
          >Sent: Dec 2, 2006 5:22 PM
          >To: toyota-prius@yahoogroups.com
          >Subject: [toyota-prius] Re: Why does using higher octane fuel cause the check engine light on the prius?
          >
          >I like it. "Behiving" obviously means the car is driving as sweet as
          >honey.
          >
          >--- In toyota-prius@yahoogroups.com, pmb <PriusPete@...> wrote:
          >
          >> In future, though you do want to find the real cause, avoid a tow by
          >trying the re-boot (simply, re start the car), and if it 'feels' like
          >it's behiving normally, just drive on.
          >>
          >> Pete
          >>
          >
          >
          >
          >To access group's website features such as Files, Photos, Links, Database and Polls, go to
          >http://autos.groups.yahoo.com/group/toyota-prius
          >, Photos, Links, Database and Polls, go to
          >http://autos.groups.yahoo.com/group/toyota-prius
          >
          >Yahoo! Groups Links
          >
          >
          >
        • Michael Pardee
          ... has ... the ... car ... you ... More technically, it has a higher self-ignition point. (Flash point is the temperature at which the liquid will produce
          Message 4 of 10 , Dec 3, 2006
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            --- In toyota-prius@yahoogroups.com, "Larry Finch" <finches@...>
            wrote:
            >
            >
            > Daniel answered your octane question accurately. Higher octane gas
            has
            > a higher flash point. It doesn't help the engine in any way unless
            the
            > compression ratio is higher than that in the Prius. Calling it
            > "premium" is marketing, or an affectation of the oil industry; the
            > only thing Premium about it is the price. Even modern cars that
            > specify premium will run on regular, because the "computer" in the
            car
            > will sense pinging and retard the spark to prevent it. Thus, all
            you
            > lose is a little power if you use regular in a car designed for
            > premium. And you lose nothing except the cost of repairs if you use
            > premium in a car designed for regular. (BTW, the FTC has a web site
            > that explains all about premium gas:
            > http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm).
            >

            More technically, it has a higher self-ignition point. (Flash point
            is the temperature at which the liquid will produce combustible
            vapors - about -40 degrees [F or C] for gasoline.) Probably more
            significant is the way gasoline achieves the higher octane rating;
            additives are used that may not play well with engines not designed
            to deal with them.

            Mike
          • Stan Sexton
            Joe- higher octane fuel has additives to make it burn slower. Otherwise the heat and pressure of a high compression ratio (which the Prius does not have
            Message 5 of 10 , Dec 3, 2006
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              Joe- higher octane fuel has additives to make it burn slower. Otherwise the heat and pressure of a high compression ratio (which the Prius does not have because of it's modified Atkinson Cycle design) would ignite the fuel and air mixture before the spark plug could. Diesel engines use compression ignition but the fuel is injected at the point of combustion. Tetraethyl lead was used for 70 years to inhibit the effect of temperature and pressure on pre-igniting the gasoline and created a higher octane gasoline from regular the most economical way. Unfortunately, environmental concerns removed tetraethyl lead and later MTBE as ways to raise octane.
              Today, octane is raised by adding more long chain hydrocarbons to make Premium gasoline. This process does not use additives but more oil. Thus here in California, we pay a minimum of 20 cents over Regular for Premium. It used to be 5-10 cents in the days of octane additives, but more oil and more refining costs real money. I think that this price increase alone will kill Premium gas engines in many standard vehicles.
              So there are zero benefits, higher costs and possibly more issues with using anything higher octane that regular in probably any car designed for regular gas. It is possible though that older cars designed for Regular may need middle grades as octane in every grade has been reduced at least here in California. Premium here seems to be uniformly 91 octane.
              It is possible that slower burning fuel causes problems with the Prius. Additional long-chain hydrocarbons may create combustion residue.
              But Premium gas by itself contains no more BTUs than Regular Gas, unless you compress the fuel-air mixture into a tighter space, which is actally what happens when you raise compression ratios. Any compression of a gas raises temperature, and of course pressure, and that is the fundamental characteristic of a "heat engine" that produces power through the pressure of a temperature rise (Carnot Cycle).









              [Non-text portions of this message have been removed]
            • Michael Pardee
              ... Well, that s not quite right either. Under normal operating conditions the burn rate of all grades of gasoline is pretty much the same. It is only under
              Message 6 of 10 , Dec 3, 2006
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                --- In toyota-prius@yahoogroups.com, "Stan Sexton"
                <stanathomesell@...> wrote:
                >
                > Joe- higher octane fuel has additives to make it burn slower.

                Well, that's not quite right either. Under normal operating
                conditions the burn rate of all grades of gasoline is pretty much
                the same. It is only under critical conditions of heat and pressure
                that octane rating is important. If the compression heating is too
                great for the octane value, the reaction propagates by the pressure
                front rather than the flame front and produces what we know as
                detonation. It is ungodly destructive because the pressure front
                strengthens as it goes and can break things. I once overhauled a
                Volvo engine that had detonated badly for way too long; the top
                compression ring in each cylinder except one was broken, some into
                three or four pieces.

                This whole subject has more room for misunderstanding than any other
                automotive area I know of. Pre-ignition (also described as dieseling
                when it occurs after the ignition is turned off) is often mistaken
                for detonation. It is sometimes sensitive to octane ratings but is
                unaffected by ignition timing because the fuel is already burning
                when the ignition fires. My dad's old VW would idle indefinitely
                after the ignition was turned off... and it was whisper-quiet that
                way.

                Suffice it to say we should only put 87 octane (regular grade) in
                the Prius.

                Mike
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