87 Octane Question
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This is a discussion on 87 Octane Question within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; I won't go into the details of how it happened (mostly because it involved no small amount of personal stupidity), ...

  1. #1
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    87 Octane Question

    I won't go into the details of how it happened (mostly because it involved no small amount of personal stupidity), but there is a tank of 87 octane gas sitting in the tank right now. I have dialed the boost down to basically 0, and have been babying the car in a (hopefully) successful attempt to hold off knocking, but my questions are:

    1) Any opinion on the safety/effectiveness of using a bottle of octane booster in this case?

    2) If I don't use octane booster, do you think it is better to fill with premium frequently to dilute the amount of 87, or is it better to take the gas almost all the way to empty (or at least past 1/4 tank) and then fill up all at once?

    All in all (given I originally thought that having 87 "swill" feeding my rex would be the end of the world), I have been surprised at how well it has run on it. Haven't had any knocking, etc.

    Thanks for any help!

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  3. #2
    Registered User SonicYellowWRX's Avatar
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    i say run a bottle of good octane boost and run out and get some of the highest octane unleaded fuel (100 octane race gas if available) to mix in with the 87. better safe than sorry, ya know.
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    Registered User pace's Avatar
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    I agree. It sounds as though your car is doing fine, but I don't know how heavily/lightly modified it is..? If this happened to me, I'd baby the car down to 3/4 tank and then get some 100 octane race gas in there.

    Alternatively, syphon that cr*p outta there. A mouthful of gasoline is an experience you will never forget, and is better than the most potent mouthwash that your dentist will ever recommend.

    -Pace

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    where can i grab some 100?

    100 octance gas would be great right around now. Any idea where I should look to get some 100 octane gas in No. VA? I am afraid that to find some at a track, I would have to drive far enough away that I might as well just wait to fill with premium from the local pump.

    I think I will take the advice and grab a bottle of octane booster. Anyone know of a good brand that won't leave too much in the way of spark plug deposits, etc?

    Thanks for the help!

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    My rex is only lightly modded, with a mbc and an up-pipe. That probably has a good bit to do with my not having too much problem (not like I was going to try to run 16 + psi on 87 anyways). And I also hope that ANY widely sold car would not suffer catastrophic engine failure just from running low octane gas, but then again, you never know I guess.


    oh, and I already tried offering my brother 10 bucks to siphon the gas from my tank. He politely declined. I told him he was passing up 10 bucks just for breathing in for a couple seconds. He remained unconvinced.

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    Registered User djrez4's Avatar
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    you could get some toulene from a paint store. it's about 114 octane. just do the quick calculation

    (gallons of crap x 87) + (gallons of toulene x 114) = total gallons x new octane rating

    so to get back up to 91 octane, you need to get your tank down around 13 gallons of 87 and fill up with toulene.
    Last edited by djrez4; 08-18-2002 at 10:26 PM.
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    Registered User SonicYellowWRX's Avatar
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    try searching on www.76.com for a location near you that carries 100 octane. My advice is to call the gas station first because it has steered me wrong twice so far. (those locations USED to carry it)

    as far as octane boost, I have been using Turbo 108 in the yellow bottle for quite some time on my Integra. It seemed to work better than NOS or any other brand out there and is quite affordable. (NOS Race Formula works as well but costs like $12 a bottle. Turbo 108 works just as well and costs $3)
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    thanks for the heads up, sonic.

    djrez, is the thing about the toluene for real? if so, that's pretty cool. I could have just been feeding my car from out of my lab hood the whole time!

    Thanks again, guys

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    Registered User djrez4's Avatar
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    Originally posted by yihoo


    djrez, is the thing about the toluene for real? if so, that's pretty cool. I could have just been feeding my car from out of my lab hood the whole time!
    yup...it's true...just don't run it too much....the chemical tends to dry out the rubber in the fuel lines.
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    Registered User SonicYellowWRX's Avatar
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    yeah i heard about toulene too, but i never tried it so i cant personally recommend it.
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    Moderator GV27's Avatar
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    a little late, but....

    The ECU has anti-knock software. Check your owners manual. A tank of 87 octane won't hurt a thing. It'd probably be fine at 16psi (but run like crap) but if you have it all the way down to 8 psi it'll run fine on 87 octane. Heck, at 8psi 87 octane is totally appropriate. The premium is only for running 14 psi!
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    Registered User PlatinumWRX's Avatar
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    Originally posted by yihoo
    thanks for the heads up, sonic.

    djrez, is the thing about the toluene for real? if so, that's pretty cool. I could have just been feeding my car from out of my lab hood the whole time!

    Thanks again, guys
    Toluene is the equivalent of 107 octane. DO NOT RUN IT STRAIGHT. Mix it with fuel.

    ANOTHER THING: Spill it on the paint and you'll be VERY SORRY.

    I use a rag around my filler neck and a LONG ASS FUNNEL to put my race fuel in.

    BTW, DP racing sells "import" 104 octane for $5.00 a gallon at most tracks.

    -Jim

  14. #13
    Registered User KanosWRX's Avatar
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    If you can't find anything close to 100 octane, their is a sunoco down main street near farish subaru. atleast their you can get 94 octane. if you have about half a tank left you can equal it out to about 91 octane.


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  15. #14
    Registered User djrez4's Avatar
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    Originally posted by PlatinumWRX


    Toluene is the equivalent of 107 octane. DO NOT RUN IT STRAIGHT. Mix it with fuel.

    ANOTHER THING: Spill it on the paint and you'll be VERY SORRY.
    -Jim
    oops....my bad 114, 107....whatever

    and yeah....what Jim said about the paint. after all, toulene is a paint remover. about 2 gallons toulene/tank of gas is about the max you should run....
    Deliberating enclaves of like-minded people are often a breeding ground for extreme movements - Cass Sunstein

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    thanks for all the help, guys!

    I went ahead and ran some octane booster (still a little wary about how clean toluene combusts), and have gotten the gas down to about 1/4 tank. I went searching for some 100 octane locally and had a bit of trouble. Will try out that Sunoco. After i get some good grade gas in the car, plan to reset ECU just in case the anti-knock sensor has messed with timing or anything.

    Babying the car for the past 250 miles has been an exercise in patience, to say the least.

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