Octane rating and ethanol...
Thread Starter
Staging Lane
Joined: Jun 2011
Posts: 84
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From: Middle TN
Octane rating and ethanol... So this gas station down the road from my house has started offering non ethanol 90 octane. I use 93 octane with the normal 10% mix we've all been plagued with. My question is, will I see any benefit to using the non ethanol 90 octane or should I just stick to 93?
Stick with the 93. Octane is simply a fuel's resistance to detonation and pre-ignition. It doesn't matter how they get to the rating, so it's really the number that matters.
Thread Starter
Staging Lane
Joined: Jun 2011
Posts: 84
Likes: 0
From: Middle TN
I see what youre saying. To clarify it was less about the octane rating than it was the lack of ethanol. These engines advance timing when using a lower octane fuel, right? But in any case the reason for my question was we've had numerous two stroke cutsaws at work bite the dust supposedly due to higher water content in ethanol blended fuel. They also run (noticeably) better when run on non ethanol fuel. I assume even though there's differences between two and four stroke engines, this may apply.
My purpose for mentioning the ratings is I wanted to know if the decrease in rating would negate the lack of ethanol, as opposed to sticking to the 93 blended fuel.
Or if this "myth" I keep hearing about ethanol blended fuel being terrible for internal combustion engines that aren't built for it is just a crock of **** put forth by corn haters or something
My purpose for mentioning the ratings is I wanted to know if the decrease in rating would negate the lack of ethanol, as opposed to sticking to the 93 blended fuel.
Or if this "myth" I keep hearing about ethanol blended fuel being terrible for internal combustion engines that aren't built for it is just a crock of **** put forth by corn haters or something
I see what youre saying. To clarify it was less about the octane rating than it was the lack of ethanol. These engines advance timing when using a lower octane fuel, right? But in any case the reason for my question was we've had numerous two stroke cutsaws at work bite the dust supposedly due to higher water content in ethanol blended fuel. They also run (noticeably) better when run on non ethanol fuel. I assume even though there's differences between two and four stroke engines, this may apply.
My purpose for mentioning the ratings is I wanted to know if the decrease in rating would negate the lack of ethanol, as opposed to sticking to the 93 blended fuel.
Or if this "myth" I keep hearing about ethanol blended fuel being terrible for internal combustion engines that aren't built for it is just a crock of **** put forth by corn haters or something
My purpose for mentioning the ratings is I wanted to know if the decrease in rating would negate the lack of ethanol, as opposed to sticking to the 93 blended fuel.
Or if this "myth" I keep hearing about ethanol blended fuel being terrible for internal combustion engines that aren't built for it is just a crock of **** put forth by corn haters or something
I see where you're going with this!
A few points:
The PCM will pull ignition timing when it hears knock. This is how it can compensate for lower octane fuel...It doesn't directly detect the octane of the fuel.
As for ethanol being "bad" for the car, I'm pretty sure that everything built in the past 10 years can handle E10 without any corrosion issues. Higher levels of ethanol can and do cause problems.
Now, from a drivability standpoint, a non-ethanol fuel will always run better than an ethanol blend of the same octane rating, again, assuming the fuel system is designed and the PCM optimized for gasoline. One example of this is fuel economy, which drops noticeable once you start adding ethanol.
On the flip side, if a car is setup for higher concentrations of ethanol (E85, etc.), then you can definitely take advantage of the higher octane ratings of well over 100 RON.
Anyway, I know this was more of an explanation than you were probably asking for, but I'll leave you with this:
For your car, 90 octane is not sufficient to prevent knock, while the 93 octane blend is. You will likely get slightly worse fuel mileage with the 93 due to the ethanol content, but at least you won't be running near constant knock retard.
Staging Lane
Joined: Dec 2010
Posts: 99
Likes: 0
From: Buffalo, NY
I used to use 93 E10 for over a year and I averaged 19.1 mpg. Three months ago I switched to 91 E0 offered at the Noco I drive past every day goiing to and from work. My average mpg is now consitantly 20.4. I used my car only for drive to and from work five days a week. 15.7 miles each way; 60% highway and 35% suburan and 5% city.
As long as its not 120 degrees outside and you do not live in a location 6k feet below sea level, you will probably not get knock retard with 90 octain fuel. In places like Denver they sell 85 octane fuel and it runs just fine in cars calling for 87 because of the higher elevation.
I am a quiet supporter of E0 getting better gas mileage than E10 (this means I do not like to debate or preach). I have my own experience and it is also noted that gasoline has more joules of energy per unit vs enthonal. The question is, is it worth the extra 40 cents more per gallon? In my case, I simply do not care and I just like running E0 because it makes me feel good
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As long as its not 120 degrees outside and you do not live in a location 6k feet below sea level, you will probably not get knock retard with 90 octain fuel. In places like Denver they sell 85 octane fuel and it runs just fine in cars calling for 87 because of the higher elevation.
I am a quiet supporter of E0 getting better gas mileage than E10 (this means I do not like to debate or preach). I have my own experience and it is also noted that gasoline has more joules of energy per unit vs enthonal. The question is, is it worth the extra 40 cents more per gallon? In my case, I simply do not care and I just like running E0 because it makes me feel good
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