# Gas octane 91 94 ?



## minesmoria (Jun 22, 2004)

My husky 55 saw manual says use 90 octane or even higher if delimbing, if you go below 90 you can over heat the engine and cause detonation.

So i guess i should use 91 octane or 94 chevron?

And if you use a gas treatmnet the gas should stay fresh for a few months longer?


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## hankster (Jan 1, 1998)

Since 91 is above 90 you can use it. Spending more for higher octane is just wasting your money. I would stay away from gas treatments. If your gas is getting old (more then a couple months) then put it in the tank of your car and buy new.


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## salsahh (Aug 19, 2004)

There is nothing wrong with using a gas treatment in your engine wether you dump it out or not the residuals left behind and in the carbuerator can varnish as well not to mention today's oil refinery's are running at near 97% capacity and the quality of fuel being distributed is terrible here read this.
http://www.sfrcorp.com/notice.asp?NoticeID=4

As for Octane this is a mis conception that everyone makes the Hankster is right. more unless needed is a waste of money and is worse than lower octane fuels

two things HIGH altitude if you live high then by low cause unless your mower is supercharged its only running at -10% for every 1000feet of elevation. 

Low Octane fuels are more volatile and burn quickly. 
High Octane fuels are less volatile and burn slower. 

Don't think that slower is necessarily better some say mileage improves but the need for a injector cleaner or fuel treatment becomes a necessity because of deposits left behind.

Compression is the real question and answer for octane most newer cars run higher compression then older ones I know i'm talking cars but the same principles apply to any 4cycle engine. Higher compression means more heat if you heat the fuel prior to ignition you have whats called pre-detonation or ping. If its severe enough and continued long enough you can experience serious engine damage. 

Lower compression engines don't have the extra heat so they are less effected by this. Most small engines are fairly low compression engines therefore the need for higher octane fuels are less. 

Diesel engines run entirely on compression most cars are like 9:1 or 10:1 most diesels are 18:1 or 20:1 and higher. gas explodes under a flame source diesel must be heated to ignite.

I hope this sets things a little straighter. 

Gas treatments are much more needed than one may think. Deposits lubrication and fuel stability are what most brands of gas sold are not acknowledging because the gas additives add cost to fuel and they're to busy making money to give it away to someone else Mobil/Exxon MADE a billion dollars each quarter this year Not took in a billion PROFITED 1 billion.


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