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Octane?

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John Wheeler

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I happened to catch in one of the manuals that it recommends 93. How true is this? I have been running 87 by default and ignorance. Should I change fuel? Tune up is coming regardless. Thanks
 

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1811Cub

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Back then, the octane listed on the pumps was listed using the research method. Today, the octane number is an average of research and motor octane numbers (R+M/2). Modern 87 octane is more than adequate for the low compression ratios normally found in these small air cooled engines. What to be concerned with most is the ethanol amount in the fuel. For these older machines, lower or none is preferred. Use Stabil if the machine is expected to sit for a while.

I use Rec fuel, which is 90 octane non ethanol blend fuel, and have zero carburetor failures or performance issues.

Gasoline explained - octane in depth - U.S. Energy Information Administration (EIA)
 

digger

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I happened to catch in one of the manuals that it recommends 93. How true is this? I have been running 87 by default and ignorance. Should I change fuel? Tune up is coming regardless. Thanks
Best to run Non-oxygenated gas no matter the octane rating. It has no additives to screw things up in the engine, and it reduces the corrosion, and doesn't eat the rubber components in the system.
 

John Wheeler

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Best to run Non-oxygenated gas no matter the octane rating. It has no additives to screw things up in the engine, and it reduces the corrosion, and doesn't eat the rubber components in the system.
Non oxygenated? Also, I go through a ton of fuel right now and it doesn’t sit for long. I’ll be doing a rebuild this spring, so maybe then?…
 

Bill Houk

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All I've run in all my tractors and every other small engine I own is Recreational Gas and NO ADDITIVES with great success over the last 6 years and I've not rebuilt 1 carburetor since.
 

PACub100

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I run 93 (well, I'm supposed to, many times it's 89) in the Volvo so I fill my jugs up with that and use in my 1450. Using it regularly doesn't let the junk in today's gas mess with the system.
Now in my weed whacker and chainsaw, I only use store bought, premixed gas because I enjoy using them about as much as I enjoy trimming my nose and ear hairs...
 

John Will

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The way it was worded to me in the service schools is "midgrade fuel" or middle button on the pump. No discount fuel due to the additional dirt and ethanol they would have. Also has been worded as " if the pump does not have three buttons for the tree levels of fuel, do not buy fuel there".
 

David Autry

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High test is made for high compression engines, it burns much hotter than regular. No need in overheating a low compression engine with high test. Here gogas sells E free high test, while circle K sells E free regular.
 

mgonitzke

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High test is made for high compression engines, it burns much hotter than regular. No need in overheating a low compression engine with high test.

This is 100% false. Higher octane = more resistance to detonation, which is why it is used in high compression engines. It does not burn hotter than regular. You will hurt nothing running high octane gas in a low compression engine other than your wallet.
 

jkoenig

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Jim Koenig Halfway between Harvester, MO and Cadet, MO
I have heard that higher octane burns longer and that could be where the added heat factor arises. Longer exposure to combustion could result in higher engine temps.
 

mgonitzke

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I have heard that higher octane burns longer and that could be where the added heat factor arises. Longer exposure to combustion could result in higher engine temps.

Slower, not longer. High octane gas actually has a bit less energy content than low octane.

This whole "engine runs hotter on high octane" thing is an old wives tale.
 

Bill Houk

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The whole High Octane deal is actually Backwards of what your brain wants to think.
Regular is actually More unstable and will detonate with less compression than High test.
That's why you can't run regular gas in a high performance engine, it'll explode when the piston is
only half way up the cylinder instead of the top, called Pre-ignition, knocking, piston rattle.
Regular Gas Will Harm your High performance engine, But High test will Not harm your little Kohler.
If you want to spend money for your fuel for your tractor, Buy ETHANOL FREE GAS. $4.25 Gal last I bought
two weeks ago. Needs no additives! I've been running it the last 6 yrs without any issues and haven't had to
rebuild 1 carb since.
 

digger

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The whole High Octane deal is actually Backwards of what your brain wants to think.
Regular is actually More unstable and will detonate with less compression than High test.
That's why you can't run regular gas in a high performance engine, it'll explode when the piston is
only half way up the cylinder instead of the top, called Pre-ignition, knocking, piston rattle.
Regular Gas Will Harm your High performance engine, But High test will Not harm your little Kohler.
If you want to spend money for your fuel for your tractor, Buy ETHANOL FREE GAS. $4.25 Gal last I bought
two weeks ago. Needs no additives! I've been running it the last 6 yrs without any issues and haven't had to
rebuild 1 carb since.
I do non-oxygenated and dose it with MMO for good measure. I popped two 2 year old cans just yesterday for a little sled run today. (y)
 

dgrenard

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In 1965 Dad bought a new 102, the local IH dealer sold a product called tetralene, it was supposed to help keep valves from sticking. added a1/2 cup per 5 gallons of gas. Currently I buy a non ethanal 90 octane fuel made by Country Mark with MMO . No carb issues with the Cubs, chainsaws, 140 International and my VW sand rail.
 

Stevenovick1

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I have a Ma Pa gas station near by that has ethanol free . And Race gas “ very Expensive. I mix 2 parts ethanol free to 1 part race gas. For the Ol Buick
 

Stevenovick1

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We own an Exxon . Back in the day the Ol timers who drove the tankers said when asked. Don’t use Hi test. The “plus” witch was between unlead and Hi test. Was the better gas. It had additives still in the fuel that the others did not have.
 
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