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What Octane number do you use inyour gas tank?

  • 91-93, Yea Baby!!

    Votes: 111 36.5%
  • 89, does the job, no complaints.

    Votes: 64 21.1%
  • 87, I'm poor, only wish i could use the high stuff.

    Votes: 129 42.4%

  • Total voters
    304
181 - 195 of 195 Posts

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Registered
2000 2.5RS/C BRP
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2,321 Posts
in my old 300m, i used 93 and the extra mileage washed the cost. but the 93 bumped my long term timing maps up and anytime id put 87 in it, the car would run terrible the next 100 miles until it relearned. running higher octane gas will let your car advance timing further and pick up some performance and mileage to an extent. most people argue this because they think the results are instant, they arent, the ecu takes time to readjust its maps.
That depends entirely on the car, though. Our old ECUs have a max timing map, and a small amount of adjustment per cell. They won't gain any benefit from anything above 89 (and possibly not from that either). Newer cars are different and can dynamically adjust timing to account for fuel quality.
 

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Registered
2000 2.5RS/C BRP
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2,321 Posts
when i disabled my knock sensor, i was pulling 15 degrees of timing put at wot and was still in the mid 20s. the limits pretty high, on a 97 ecu anyway
Should be +/- 15*. At high RPM the piston speeds are very high and the timing has to be pretty advanced for the flame front to expand fast enough to do sufficient work, so that sounds reasonable to me. In my car, at 6000RPM and 4 PSI, it runs 39*. Take 15 off that and you're at 24.
 

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Registered
2006 2.5i
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11 Posts
91

91. I know what the manual says, and I know the facts also. But, I just feel the car runs smoother, so it make me feel better.
 

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Registered
Joined
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39 Posts
Ethonal free 91 octane premium here in western CO! Both my 95 Legacy and my 2016 3.5 Ecoboost F150 run better and getter fuel mileage with it
 

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Boxer rumble FTW!
2005 Subaru Impreza 2.5 RS
Joined
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621 Posts
91-93 on my pump map when needed.

Most of the time E85 baby! : ) Not my everyday car, but i can drive it often with no problems just not the best mileage!
 

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Registered
2001 gm6
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103 Posts
Mixing e85 and 87 octane. Car feels a little more powerful but engine mainly feels smoother than just using 87. My01 RS, stock tune
 
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