87 octane vs 89 octane

Discussion in 'Gen 2 Prius Fuel Economy' started by y2jasmine, Jun 11, 2014.

  1. y2jasmine

    y2jasmine New Member

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    So I'm a new owner to a 2004 in Toronto, Canada... In my first half tank (last half of a tank), which had 87 octane gas, I achieved on average 6 l/km or 40mpg. Not bad I thought considering my city driving, including some minor rush hour.

    But then I had a throttle issue... Check engine light came on. It read something like a misfire or something similar, minor throttle issue regardless, so it was recommended to put 89 octane in once.

    Last night I put in 89 octane (an extra 10 cents per litre). It still had one bar left, but I filled it to a half tank. I first got 4.7 l/km but did some heavier city driving now and I am getting 5 l/km or 47 mpg.

    Am I just getting used to driving a Prius? Does my car like the higher octane? Or why such a noticeable difference... I'm confused! Has this happened to anyone else?

    Nexus 4 ?
     
  2. Chris Cote

    Chris Cote Junior Member

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    y2jasmine,
    Welcome! There is a difference in putting in higher octane fuels but, I don't think all of that gain in MPG was related to the octane change. My feeling is you got some bad fuel at your 87 octane half tank with possibly some water in it. (the most probable reason for a one time misfire). Then your driving was a bit different and that combined with the better octane made the difference. Our milage tends to increase with highway driving.
     
  3. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    There are areas of North America where 87 is E10 (with 4% less MPG than E0) while 91 is E0. (so far as I know 89 is just a mixture at the pump, there is no 89 tank at the gas station or in the truck that delivers fuel)
     
  4. Easy Rider

    Easy Rider Active Member

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    Did you look for other similar posts before asking this question ?
    It has been discussed before ........MANY TIMES.

    The short recap is:
    Not likely the gas really made any difference.......unless the 87 was E10 and the 89 was E0.

    I don't think anybody here has reported CONSISTENTLY better mileage with 89, all other things being equal, but by all means try each for a few tanks in a row and see for yourself.
     
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