STIHL USA News: STIHL MotoMix Offers Convenience and ...
www.stihlusablog.com/.../stihl-motomix-offers-convenience-and.htm...
May 19, 2011 – At STIHL our basic recommendation is that fuel be as high an octane rating as possible, at least 89, and contain no more than 10% ethanol.
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Re: Higher octane gas for lawn equipment
Posted by: "Lee Griffith" ldgriff2001@yahoo.com ldgriff2001
Date: Sat May 26, 2012 8:43 am ((PDT))
Octane rating of gasoline is often misunderstood. Gasoline is composed of different compositions of hydrocarbons produced by distilling crude oil at different temperatures to obtain these fractions. Some of the longer molecules are converted to smaller chains of hydrocarbons by "cracking" the double bonds or some of the shorter chained fractions are made longer by "isomerization." These fractions are mixed and tested in a knock engine that varies compression and compares the knocking of your mixture against a known fraction called isooctane that has a knock value of 100. Knocking is caused by pre-ignition of the fuel from the heat of compression, before the spark plug fires.
Thus, since small engines are not high compression engines, knocking should not be an issue regardless of the octane rating used. Also mixing your gasolines just creates your own mixture with your own octane number. Running engines on octane ratings higher than necessary to prevent knocking does not give more power as commonly thought.
You can learn more here: http://chemistry.about.com/cs/howthingswork/a/aa070401a.htm
-Lee
On May 26, 2012, at 7:45 AM, Doug Kalmer wrote:
>
> The ethanol in most gas is what degrades fuel lines and carb parts, avoid it for small engines and older engines. If you use the recommended octane, going to a higher grade will not harm the engine, but it just costs more. Mixing octanes is OK. Doug
>
> http://www.builditsolarblog.com/2012/03/dougs-solar-projects.html
>
> http://www.youtube.com/user/sundug69
>
> http://www.builditsolar.com/Projects/PV/DougEnphase/DougEnphase.htm
>
Posted by: "Lee Griffith" ldgriff2001@yahoo.com ldgriff2001
Date: Sat May 26, 2012 8:43 am ((PDT))
Octane rating of gasoline is often misunderstood. Gasoline is composed of different compositions of hydrocarbons produced by distilling crude oil at different temperatures to obtain these fractions. Some of the longer molecules are converted to smaller chains of hydrocarbons by "cracking" the double bonds or some of the shorter chained fractions are made longer by "isomerization." These fractions are mixed and tested in a knock engine that varies compression and compares the knocking of your mixture against a known fraction called isooctane that has a knock value of 100. Knocking is caused by pre-ignition of the fuel from the heat of compression, before the spark plug fires.
Thus, since small engines are not high compression engines, knocking should not be an issue regardless of the octane rating used. Also mixing your gasolines just creates your own mixture with your own octane number. Running engines on octane ratings higher than necessary to prevent knocking does not give more power as commonly thought.
You can learn more here: http://chemistry.about.com/cs/
-Lee
On May 26, 2012, at 7:45 AM, Doug Kalmer wrote:
>
> The ethanol in most gas is what degrades fuel lines and carb parts, avoid it for small engines and older engines. If you use the recommended octane, going to a higher grade will not harm the engine, but it just costs more. Mixing octanes is OK. Doug
>
> http://www.builditsolarblog.
>
> http://www.youtube.com/user/
>
> http://www.builditsolar.com/
>
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