Ethanol Free and Octane

Discussion in 'The Mixing shop.' started by hvramesq, May 26, 2019.

  1. hvramesq

    hvramesq Silver Level contributor

    Hi all,

    Have questions on how to get higher octane in my fuel mix.

    my car is a 70 gs 455 all stock. Most of the time, I am running ethanol free gas. However, its usually 89 octane as the vendors of 90-93 octane are not near my house. I have read on this board how octane boost is a waste of money. I do have a VP racing fuel vender about 3 miles from my office. but they have all kinds of different fuels. I am not racing the car. I just cruise around and want the fuel system and motor to be safe and have that giddie up when needed.

    so questions is: what is the economical and what is the best way to boost octane when running 89 ethanol free gas from WAWA.

    thanks, hvramesq
  2. flynbuick

    flynbuick Super Moderator Staff Member

    Go to your local small airport and buy some 100 ll Avgas. You will need some 5 gallon cans. They will not pump it into your car.
    Brett Slater likes this.
  3. hvramesq

    hvramesq Silver Level contributor

    Hi Jim, are you suggesting running avgas straight? or mixing with ethanol free? what mix-3:1?
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Figuring octane is easy, just a simple average. Figure out what octane you would like to run. Then just grab your phone and use the calculator. Say you want to run at least 94 octane. Let's try some 110 leaded race gas. Figuring a 20 gallon tank, lets try 5 gallons of 110.

    15 X 89 = 1335

    5 X 110 = 550

    1335 + 550 = 1885

    1885/20 = 94.25
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

  6. hvramesq

    hvramesq Silver Level contributor

    thanks Larry!
  7. shiftbyear

    shiftbyear Well-Known Member

    I wrote to VP racing fuels in regards to using Avgas 100LL in classic cars, I've used it myself. Here is the reply:

    Several reasons that 100LL is not good for automobiles. Very little to no lubricant in the fuel so it is very will not give enough protection to valve seat and guides and will have increased cylinder wall wear. The normal operating range for this fuel is idle to 3500 max RPM because that's all the RPM's that aircraft engines turn so the burn speed is optimized for high RPM applications. And lastly tuning can sometimes be difficult because the fuel is designed to be used at 10,000-30,000 feet the tuning window can be very small.

    Tom Henriott
    Race Fuel Tech
    VP Racing Fuels
  8. Doo Wop

    Doo Wop Where were you in '62?

    Here's my formula.
    94 octane by 15 gallons = 1410
    110 octane by 5 gallons = 550
    Octane result 1960 divided by 20 = 98 octane per gallon.

    You can always use toluene or xylene instead of 110. That will give you 99.5 octane.
  9. tsgp51

    tsgp51 Well-Known Member

    As Maverick said I think the data on av gas is inaccurate. I'm not a scientist but burned valves and scored cylinder walls would be bad at 4500 feet .Also 99.9 %of piston driven airplanes fly below 10000 feet because they are not pressurized. I ran it in my turbo regal,worked fine (except for the o-2 sensor) I also mix it in my gsx I Think av gas doesn't have the light hydrocarbons of auto gas so it's harder to start in the cold ,but you don't want vapor lock while you are flying
    Mike B in SC likes this.
  10. flynbuick

    flynbuick Super Moderator Staff Member

    As a longtime pilot I must roll my eyes a bit at his statement that Avgas is designed for 10 to 30k feet. 99 % of piston aircraft are flown below 10k feet. Plus the most critical time to keep the engines running is during take off when one is at the lowest altitude.

    99% of piston aircraft allow the mixture to be manually adjusted by the pilot in flight and on the ground. The prime directive of Avgas is to not let the engine detonate. It is highly leaded for this reason.

    When I see Avgas described a “dry”, I always think this description originated as a referral to its lack of water content. This is intentional. Its handling and segregation from other fuel stocks is meant to keep water content as low as possible. The reason is to prevent the fuel from freezing while flying at altitudes where it is often very cold. (The adiabatic lapse rate for temperature is an average of 3 degrees per 1000 feet of altitude) If the fuel freezes due to water content the engines suddenly stop.

    Last edited: Jun 1, 2019
    1972Mach1 and Mike B in SC like this.
  11. NZ GS 400

    NZ GS 400 Gold Level Contributor

    Well, I am sure that VP would prefer that you buy their fuel, not AV gas. I can't help but wonder if that fact has anything to do with their scare tactics type answer.
    Gallagher and DasRottweiler like this.
  12. hvramesq

    hvramesq Silver Level contributor

    i gues if there is anything to this "dry" no lubrication issue it is solved by running a blend of no more that 3:1 100ll
  13. shiftbyear

    shiftbyear Well-Known Member

    Sorry didn't mean to ruffle any feathers, I have no problem using avgas myself, but it may not be the best choice. I just sent a email to Sonoco on the subject, just waiting for a reply. Downloaded this from their Tech menu, not pertinent to this post but good info.
  14. NZ GS 400

    NZ GS 400 Gold Level Contributor

    Thanks for the link. Interesting read.
  15. flynbuick

    flynbuick Super Moderator Staff Member

    No feathers here. The lead compound in gasoline was removed for public health reasons and not because it was not effective. We still use it in piston aircraft because we use 1930s ignition—magnetos with fixed timing at about 22 degrees.
  16. DasRottweiler

    DasRottweiler -BuickAddict-

    Simply this for me if you would please, when I pull up to the fuel shack at the drags, which VP
    fuel do I ask for ?. I use 91 to 93 octane pump gas in an iron headed mild cam 9 to 1 462. Looking for detonation protection rather than et/mph improvement. More information, my AEM AFR gauge instructions say no leaded fuels as leaded fuel will destroy the sensor. I have run the eth-free in my 78 Johnson outboard 2 cycle and love it, but its not an option for the 70' if it is a leaded fuel.
    Thanks.... Jim
    Last edited: Jun 2, 2019
  17. telriv

    telriv Well-Known Member

    In your case for detonation protection I would retard the timing a few degrees since you have, really, no other choice or just remove the O2 if you feel your AF ratios are OK.
  18. DasRottweiler

    DasRottweiler -BuickAddict-

    So, you are saying all VP racing fuel is leaded?
    And if I were to run racing fuel mixed with 93 octane unleaded ethanol premium to yield me an octane rating around 98 could I simply plug my sensor bung , pop the fuse that feeds the AFR gauge and rock and roll ?
    Or perhaps thete is another option where I could retain the AFR guage without reducing timing and therefore performance? Jim
  19. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    No, their C10 is unleaded and 100 octane. If you want a higher octane, you'll need a leaded fuel. When I know I will be running leaded fuel, I remove the sensor and plug the bung. No need to remove a fuse on the gauge.
  20. DasRottweiler

    DasRottweiler -BuickAddict-

    Ok, so C10 in the appropriate amount to yield me 97-8 would be great then, allowing me to tune with the help of the AFR guage. I'll have no need to obtain any more octane than that. It will also allow me to bump timing to take advantage of the additional octane, instead of going the other way.
    Thanks again Larry. JIM

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