Why would my 99 Suburban run better on 87 octane?

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by i_build, Jun 14, 2010.

  1. i_build

    i_build Rockstar

    For about a year now everytime she sits in traffic for a bit, I get an intermitent miss... especialy if I have the A/C on. After stopped for a bit upon initial acceleration she misses until she rolls a bit. Fuel pressure good (new pump), new plugs cap and rotor about a year ago. I always put in High test or mid grade.

    This morning I was low on cash so I got the cheapest gas. I drove to work... and not one miss. I drove back in about 100* weather in traffic... and not one miss.

    What happened? I think I read lower octane means the gas will ignite easier... does this imply that I have an ignition issue?
    Last edited: Jun 14, 2010
  2. Naptime

    Naptime Rockstar 100 Posts

    I tried a few tanks of the good stuff in mine too. No question it runs better on the cheap stuff. I wrote it off to computer and timing setup for that grade.
  3. i_build

    i_build Rockstar

    Thanks. Good to know I'm not the only one who noticed this. Thought I was treating her right feeding her the higher octane. It's been a few days now and I still havent felt 1 miss.
  4. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    why would my 99 suburban run better on 87

    Unless you have a performance tune installed than 87 is what your stock computer and truck was tuned for.Save your money.
  5. i_build

    i_build Rockstar

    I could have saved a nice chunk of change. Dont know why I never seen a post about this before... but I have seen a boat load of intermitent idle miss posts...

    Thanks... is this in the faq or sticky sections?
  6. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    Simple rule of thumb, always use the lower octane stuff on factory UNLESS the owners manual specifically says to use higher octane. Higher octane needs higer temps to burn off completely, along with upgraded ignition, plugs and so on.

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