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Gasoline Octane and Performance

Discussion in 'Performance' started by Arty, May 22, 2021.

  1. Arty

    Arty Active Member

    Until yesterday, I have always used just regular 87 Octane unleaded in my 1992 Mitsubishi MiniCab.
    On a whim, I filled up using Shell 91 Octane, and without paying really close attention, I began to notice that my little buddy seemed to be acting a bit different. - - Just more perky, and generally seemed to be more powerful, and generally in a really happy mood.
    I know this sounds a bit goofy, and I'm also aware that unless an engine actually needs it, using higher octane fuel will do nothing, but damn - - it actually seemed to make a difference. - - Enough that I think I'll continue to use the 91 Octane, even though it costs quite a bit more. - - After all, these things do get pretty decent mileage anyway, so the cost won't kill me.
    Am I just blowing smoke, or has anyone else found similar results?
     
    Last edited: May 22, 2021
  2. Limestone

    Limestone Well-Known Member

    Arty,
    No!!! You are not blowing smoke! Seriously! As mentioned before, the fuel that were buying today is really pretty inferior, and with all the Ethanol, and other Garbage that the, Multi Billion Dollar Fuel Corporations, keep jamming down our throats, that our Crooked political Government can give two sh*&'s about, is just good enough to start your motor with, but will still cause you a lot of problems. With fuel additives such as Stabil, Sea Foam, too name a few, that do help, Instead, a Higher octane, more expensive, fuel with cause you a lot less problems, now and down the road! Several of the people, and friends that I deal with, have had this very discussion for years, and to be honest, I've switched to the higher octane fuel years ago, and it really helps, and I can tell the difference in using it! I also keep a 5 gallon can of 110 octane Racing Fuel on hand, @ about $ 8-9, bucks a gallon, I put a small dose in my small motor cans, and before I park my small motor, yard equipment for winter,(about 5 months), I dose everything with a little Racing fuel, and I don't have issues at all!!! Getting back to your OP Question, YES,YES, YES, I've noticed the difference!!! A much more improved difference in performance, and it's really nice when all, and I mean ALL my small motors start, on one pull!
    Limestone
     
    Last edited: May 22, 2021
  3. Arty

    Arty Active Member

    Thanks for the reply Limestone. From now on, it's 91 Octane or nothing. - - Another trick I use, is Napthalene based moth-balls. - -One ball per 5 gallons. - - - Sounds stupid, but it works.
     
  4. Limestone

    Limestone Well-Known Member

    Yeah, the old Racers trick! Never tried it, but I remember you mentioning it before, and I did ask a few old Race buddies, and they were familiar with it! My wife who is very Frugal, in many good ways,(lol)! Thinks I'm nuts anyways, can't stand wasting money! I always go into details, on some of the saved $, project! lol! After 39 yrs. were still able to laugh about the dumb stuff! Oh don't get me wrong, she's talked me off the ledge a few times! lol! Especially, when it comes to one of my long time passions of Collecting old Winchesters! lol!
    Limestone
     
  5. Arty

    Arty Active Member

    One last follow-up. - -I took my Mini out today on some errands, and yes - it does run better. On 87 grade, I was noticing kind of a rattle on cold start - gone. Hot start seems better too (probably less vapor-lock). And it seems to have added just enough more power to make the thing way more fun to drive. - Just an all round happier camper.
    Now I feel like a tool for having fed my little buddy crap food all winter. - No more.
     
    Last edited: May 24, 2021
  6. Jigs-n-fixtures

    Jigs-n-fixtures Well-Known Member

    Rules of thumb at sea level
    9:1 or less compression, run 97 pump octane,
    9:1 to 10:1 compression, run 98 pump octane,
    10:1 to 11:1 compression, run 99 pump octane,
    if you go up in altitude you can decrease it by one pump octane number per 2000-ft.

    I think most of the minitrucks are at about 9.5:1 to 10:1. My S110P, has a 9.5:1 compression ratio, I run 97 pump octane at 4000-ft.
     
  7. Arty

    Arty Active Member

    Thanks Jigs.
     
  8. Limestone

    Limestone Well-Known Member

    Arty,
    How else would you know if you didn't try one way or another? Now you know, and you won't go backwards!:)
    Limestone
     
  9. coffeemaker

    coffeemaker New Member

    Carburetted engines should not stored with ethanol contaminated fuel. It oxidizes and clogs the fuel jets.

    Still, it is the politicians and EPA bureaucrats (aided by farmers' lobbying) that force ethanol in gasoline, not the oil companies. An oil company sells less fuel when some is displaced by ethanol, making less profit; they have no incentive.

    Unfounded speculation is not helpful.
     
  10. t_g_farrell

    t_g_farrell Member

    Also, just to add on here. The fuel grades in Japan starts at around our mid level (89-91) octane. So it makes sense these engines run better with fuel at that grade. I filled mine up with 91 octane and it runs a lot smoother, better. Very noticeable. So you're not imagining it Arty.
     
  11. Jigs-n-fixtures

    Jigs-n-fixtures Well-Known Member

    There are two ways octane is determined. One is the motor octane, the other is the research octane. In japan the octane rating is just the reserch octane number, in the US and Canada the Anti Knock Index, is shown as the octane, it is the average of the research octane, and the motor octane. Typically the RON number is about ten lower than the MON or Motor Octane Number.

    So, a recommended RON of 92 in Japan, would be a fuel with an AKI of roughly 97. A recommended 96 in Japan, would be about an AKI of 101. A recommended RON of 90 in Japan, would correspond to an AKI of 95.

    The highest AKI fuel I can purchase locally is a 92, which would correspond to roughly a RON of 87.
     
    Last edited: Nov 24, 2021 at 9:47 PM
    t_g_farrell likes this.
  12. t_g_farrell

    t_g_farrell Member

    Good info Jigs, I only knew they were different but not the how and why. Thanks.
     

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