Kennycash12
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Do predator motors need a 87/91 octane or is regular gas fine?
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Quick gas question
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Bbqjoe
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Whatever your lowest octane is, is just fine.
Kennycash12
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Okay cool I know some small engines hate low octane just making sure
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obone
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My Kohler manual says 87 or higher unless you live in a country that uses the research method then it's 90 minimum. (What ever the research method is). Isn't 87 regular gas?
Hellion
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Rocket fuel, FTW!
In all seriousness, avoid ethanol based gasoline if at all possible. I just tore down a nice old 1969 4hp Briggs carb that was plugged with flaky white oxidation caused by a corrosive agent (the alcohol which is ethanol) and aluminum. Bad reaction.
The rest of it was clogged with rotten gas, e.g. varnish that had the appearance and consistency of pancake syrup. Nasty!
In all seriousness, avoid ethanol based gasoline if at all possible. I just tore down a nice old 1969 4hp Briggs carb that was plugged with flaky white oxidation caused by a corrosive agent (the alcohol which is ethanol) and aluminum. Bad reaction.
The rest of it was clogged with rotten gas, e.g. varnish that had the appearance and consistency of pancake syrup. Nasty!
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Kennycash12
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Thanks for all the info guys! Much appreciated
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Bbqjoe
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At the risk of quoting myself....
Just a quick synopsis on octane. (As far as I understand it)
First, as we know, gasoline is flammable.
Diesel not so much.
The reason diesel combusts, is when it enters the cylinder, the piston comes up, creating a massively large amount of compression. This pressure creates a lot of heat which in turn causes the fuel to explode and burn.
In your basic engine, a similar reaction occurs, but using a much lower level of compression. Nonetheless, it's still a lot of pressure, but not enough to cause spontaneous combustion. That is why we use a spark to cause ignition to the fuel air combination.
If you were to expose gasoline to those extreme pressures that diesel sees, it would have a tendency to ignite without a spark, especially if the engine cylinder was quite hot.
87 octane is considered more flammable then the currently available 91-93 octanes.
Other place such as Europe, can sometimes see as high as 98 octane.
Now if you had a high end engine, possibly in the racing class, with a very high compression ratio, you might end up with 87 octane igniting somewhat earlier before the spark was sent.
It can even ignite before the piston reaches top dead center, which would then cause the energy released to try and push the piston back down, while it was still coming up.
This is very hard on the engines internals, and produces a sound known as knocking or pinging, also creating a massive loss of power.
Of course what we want is our fuel to ignite right at TDC, or just a hair after that, while the piston is free to continue its downward motion.
In higher octane, the fuel, for lack of a better term, has a burn retardant in it, so it won't so easily ignite by itself in a high compression engine.
That is all higher octane does. It doesn't contain any higher energy that that of regular gas, it just burns a little slower, and is harder to ignite.
There is no benefit to putting higher octane in an engine that does not require it.
But if we could get the cattle feed out of our gas, we would see greater energy released from our fuel, and probably even better milage.
Just a quick synopsis on octane. (As far as I understand it)
First, as we know, gasoline is flammable.
Diesel not so much.
The reason diesel combusts, is when it enters the cylinder, the piston comes up, creating a massively large amount of compression. This pressure creates a lot of heat which in turn causes the fuel to explode and burn.
In your basic engine, a similar reaction occurs, but using a much lower level of compression. Nonetheless, it's still a lot of pressure, but not enough to cause spontaneous combustion. That is why we use a spark to cause ignition to the fuel air combination.
If you were to expose gasoline to those extreme pressures that diesel sees, it would have a tendency to ignite without a spark, especially if the engine cylinder was quite hot.
87 octane is considered more flammable then the currently available 91-93 octanes.
Other place such as Europe, can sometimes see as high as 98 octane.
Now if you had a high end engine, possibly in the racing class, with a very high compression ratio, you might end up with 87 octane igniting somewhat earlier before the spark was sent.
It can even ignite before the piston reaches top dead center, which would then cause the energy released to try and push the piston back down, while it was still coming up.
This is very hard on the engines internals, and produces a sound known as knocking or pinging, also creating a massive loss of power.
Of course what we want is our fuel to ignite right at TDC, or just a hair after that, while the piston is free to continue its downward motion.
In higher octane, the fuel, for lack of a better term, has a burn retardant in it, so it won't so easily ignite by itself in a high compression engine.
That is all higher octane does. It doesn't contain any higher energy that that of regular gas, it just burns a little slower, and is harder to ignite.
There is no benefit to putting higher octane in an engine that does not require it.
But if we could get the cattle feed out of our gas, we would see greater energy released from our fuel, and probably even better milage.
Kennycash12
New member
Okay wow that makes so much sense and thank you so much for the wright up that's info google doesn't have haha
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Hellion
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See Ethanol Damage Up Close...
Other assorted articles, for the edification of all:
https://www.tractorsupply.com/know-how_home-garden_outdoor-power-equipment_ethanol-and-its-effects-on-outdoor-power-equipment
http://www.consumerreports.org/cro/news/2013/03/gas-with-ethanol-can-make-small-engines-fail/index.htm
http://www.rentalmanagementmag.com/Art/tabid/232/ArticleId/23136/Ethanol-and-small-engines-An-educate-on-fuel-usage.aspx
Other assorted articles, for the edification of all:
https://www.tractorsupply.com/know-how_home-garden_outdoor-power-equipment_ethanol-and-its-effects-on-outdoor-power-equipment
http://www.consumerreports.org/cro/news/2013/03/gas-with-ethanol-can-make-small-engines-fail/index.htm
http://www.rentalmanagementmag.com/Art/tabid/232/ArticleId/23136/Ethanol-and-small-engines-An-educate-on-fuel-usage.aspx
Panhead5496
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I had basically the same question. Read this thread. Tons of info 
http://www.diygokarts.com/vb/showthread.php?t=36744
http://www.diygokarts.com/vb/showthread.php?t=36744
Kennycash12
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Thanks! That was a good read
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Hellion
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You go over and read that, it's like deja vu all over again.
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