Originally Posted by 92saturnsl2
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I reiterate, the low compression ratio of small air cooled engines does not require a higher octane rating than 87. If a small air cooled engine had a high enough compression ratio to require higher octane fuel, you wouldn't be able to pull start it.
Regardless, if it makes you feel better using higher octane fuel, go ahead and use it, it won't hurt anything.
This just isn't true. Compression ratio and octane are not the only attributes that determine the potential for preignition. Engine/combustion chamber design (and resulting combustion stability), ignition and valve timing, air/fuel ratio, altitude, temperature and other variables come into play. Just because an engine has a lower compression ratio does not make it invulnerable to preignition.
Yes, it IS true.
I never stated that an engine having a low compression ratio is invulnerable to pre-ignition. The use of higher octane gas in-and-of-itself does not necessarily eliminate pre-ignition.
It is a FACT (not my opinion) that small air cooled OPE engines have a low compression ratio, and it is a FACT (not my opinion) that unsophisticated and relatively crude air cooled OPE engines, especially lawnmower engines (which is what the OP inquired about), do not require the use of gas with over 87 octane. Only a very small number of high performance chainsaws actually need higher octane fuel.
I am trying to educate you guys with the knowledge I have gained working in the OPE industry over many years. You can disagree with me if you want, it is up to each of you to decide whether or not I am blowing smoke, I can assure you that I am not. After disassembling literally thousands of lawnmower engines (and other small OPE engines), I never saw one that was damaged by the use of 87 octane fuel. Furthermore, I have never witnessed the improved performance of any lawnmower using higher octane gas (other than the use of E0).
Quote
I reiterate, the low compression ratio of small air cooled engines does not require a higher octane rating than 87. If a small air cooled engine had a high enough compression ratio to require higher octane fuel, you wouldn't be able to pull start it.
Regardless, if it makes you feel better using higher octane fuel, go ahead and use it, it won't hurt anything.
This just isn't true. Compression ratio and octane are not the only attributes that determine the potential for preignition. Engine/combustion chamber design (and resulting combustion stability), ignition and valve timing, air/fuel ratio, altitude, temperature and other variables come into play. Just because an engine has a lower compression ratio does not make it invulnerable to preignition.
Yes, it IS true.
I never stated that an engine having a low compression ratio is invulnerable to pre-ignition. The use of higher octane gas in-and-of-itself does not necessarily eliminate pre-ignition.
It is a FACT (not my opinion) that small air cooled OPE engines have a low compression ratio, and it is a FACT (not my opinion) that unsophisticated and relatively crude air cooled OPE engines, especially lawnmower engines (which is what the OP inquired about), do not require the use of gas with over 87 octane. Only a very small number of high performance chainsaws actually need higher octane fuel.
I am trying to educate you guys with the knowledge I have gained working in the OPE industry over many years. You can disagree with me if you want, it is up to each of you to decide whether or not I am blowing smoke, I can assure you that I am not. After disassembling literally thousands of lawnmower engines (and other small OPE engines), I never saw one that was damaged by the use of 87 octane fuel. Furthermore, I have never witnessed the improved performance of any lawnmower using higher octane gas (other than the use of E0).