1. Attachments are working again! Check out this thread for more details and to report any other bugs.

So which fuel is it?

Discussion in 'Generation 1 Prius Discussion' started by babbles, Jan 31, 2022.

  1. babbles

    babbles Junior Member

    Joined:
    Aug 12, 2021
    38
    3
    0
    Location:
    seattle
    Vehicle:
    2001 Prius
    Model:
    One
    so the manual says
    Select unleaded gasoline with an Oc- tane Rating of 87 (Research Octane Number 91) or higher
    so which one? my daughter had been putting in 91and I didn't know it and put in 5 gl of 87 last evening, will there be an issue?
     
    #1 babbles, Jan 31, 2022
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    110,133
    50,049
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    no issues either way. 87 is all that is needed
     
    #2 bisco, Jan 31, 2022
  3. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    7,035
    2,790
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    In the US, it is 87.
    In some other countries, the exact same fuel is labeled 91......because the measurement systems are different.
    87 is right.
    91 is overkill.
     
    #3 sam spade 2, Jan 31, 2022
  4. babbles

    babbles Junior Member

    Joined:
    Aug 12, 2021
    38
    3
    0
    Location:
    seattle
    Vehicle:
    2001 Prius
    Model:
    One
    ah dude! thanks much!
     
    #4 babbles, Jan 31, 2022
  5. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    24,904
    16,213
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    To get a little more of the detail behind it ...

    There are a couple ways of measuring the knock-resistance of a fuel, one that gives you the "research octane number" (R) and one that gives you the "motor octane number" (M).

    At US filling stations, the number that is used in labeling is the average of the two, (R+M) รท 2. That is typically 87 for a "regular" blend, which would have a plain R number around 91 (it follows that its M number is around 83).

    If you were in a country that labels fuel with the straight R number, you would look for 91.

    More here:

    Gasoline explained - octane in depth - U.S. Energy Information Administration (EIA)
     
    #5 ChapmanF, Jan 31, 2022
    ammdb likes this.
(You must log in or sign up to post here.)