Gas octanne in 3.6
07-09-2014, 04:15 AM
#21
JK Super Freak
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It's not just personal experience, it's science! Octane Rating - Understanding Fuel Octane | Exxon and Mobil
Has anyone ever seen an actual experiment/ data on this or are we all just talking anecdotally?
07-09-2014, 04:18 AM
#22
This is one of those topics that in the end, everyone will walk away with the same opinion they started with. LOL! Someone said it earlier, and I agree, there are so many variables that may make a higher octane perform better. Someone mentioned altitude, climate, engine upgrades, load (towing/ heavy foot), etc....
Who ever posted that link to the octane explanation, I read it and it's much appreciated.
I did notice it looked like a mobile/exxon sponsored page, FYI. I think what i'm experiancing is due to ethanol. I past a link below:
Gasoline Octane and E10 Ethanol Blend Fuels
We have very high humidity in SC. You can walk outside in the middle of the summer, like this time of year, at mid night and instantly get swamp ass. A lot of moisture in the air. I mentioned previously that I try to run strait gas when I can. I did fail to note that when I find strait 87 octane it runs just as good/efficient as it does with E10 at 89 or 93 octane. I also don't have a 6th gear since I have a tad taller tire and 3.21 gears, so another factor on my end may be that i'm harder in the gas at times than I would be if I had proper gearing. Just tossing stuff out there. I'm no scientist, just a redneck from SC.
Who ever posted that link to the octane explanation, I read it and it's much appreciated.
I did notice it looked like a mobile/exxon sponsored page, FYI. I think what i'm experiancing is due to ethanol. I past a link below:Gasoline Octane and E10 Ethanol Blend Fuels
We have very high humidity in SC. You can walk outside in the middle of the summer, like this time of year, at mid night and instantly get swamp ass. A lot of moisture in the air. I mentioned previously that I try to run strait gas when I can. I did fail to note that when I find strait 87 octane it runs just as good/efficient as it does with E10 at 89 or 93 octane. I also don't have a 6th gear since I have a tad taller tire and 3.21 gears, so another factor on my end may be that i'm harder in the gas at times than I would be if I had proper gearing. Just tossing stuff out there. I'm no scientist, just a redneck from SC.
07-09-2014, 05:55 AM
#24
JK Enthusiast
That link is nothing close to science lol. It says very generically " ordinarily USing higher octane fuel will not effect performance". To me this reads: in extraordinary cases you may get better performance with better fuel.
Has anyone ever seen an actual experiment/ data on this or are we all just talking anecdotally?
Has anyone ever seen an actual experiment/ data on this or are we all just talking anecdotally?
The science is in the calculation of the rating itself. By definition, it is a measure of the fuel's stability under compression to resist pre-ignition (knocking). It is not a measure of energy contained (heating value).
Gasoline has an energy content or Low Heat Value of 20,400 BTU/lb. Ethanol is 12,412 BTU/lb. But Ethanol has a higher octane rating - 99.15 AKI. This is why ethanol is blended with gasoline at up to 10% concentration at most US pumps. It's a cheap and relatively clean way to increase the octane rating of gasoline. We used to add lead to gas to do this, but then we figured out that was pretty bad on the environment and thus all on-highway gasoline is referred to as unleaded. The ethanol blend nets you a lower MPG because it contains less energy, just ask anybody that has used E85 in a flex fuel vehicle.
If you want to believe that higher octane fuel gives you better mileage, I won't argue, because you don't understand what octane rating even is. And I'll just watch my stock in oil companies continue to climb.
07-09-2014, 06:47 AM
#26
The link is an Exxon/Mobile page discussing the definition of octane rating and the fact that is has nothing to do with the energy contained in the fuel. I just figured I would include it since one of the major manufacturers of gasoline has on their own web page that higher octane gas than the engine is designed for will not net you any benefit. It would be in their interest to hype the higher octane (more expensive) fuel if they could legally say it would help performance. The science is in the calculation of the rating itself. By definition, it is a measure of the fuel's stability under compression to resist pre-ignition (knocking). It is not a measure of energy contained (heating value). Gasoline has an energy content or Low Heat Value of 20,400 BTU/lb. Ethanol is 12,412 BTU/lb. But Ethanol has a higher octane rating - 99.15 AKI. This is why ethanol is blended with gasoline at up to 10% concentration at most US pumps. It's a cheap and relatively clean way to increase the octane rating of gasoline. We used to add lead to gas to do this, but then we figured out that was pretty bad on the environment and thus all on-highway gasoline is referred to as unleaded. The ethanol blend nets you a lower MPG because it contains less energy, just ask anybody that has used E85 in a flex fuel vehicle. If you want to believe that higher octane fuel gives you better mileage, I won't argue, because you don't understand what octane rating even is. And I'll just watch my stock in oil companies continue to climb.
07-09-2014, 09:39 AM
#28
JK Enthusiast
Not even close to the point of the post, but since you mentioned it, here is how it IS related.
Lead in the form of tetraethyllead was added to gasoline to increase octane until the 70's.
Now other additives are used and we call it unleaded.
Ethanol is one of these additives used to increase octane. One method is to add it in the form of MTBE, made by synthesizing ethanol and isobutylene. (But other methods are generally cheaper)
When adding anhydrous ethanol (as in today's ubiquitous E10 gasoline), it raises the octane rating by a couple points.
Lead in the form of tetraethyllead was added to gasoline to increase octane until the 70's.
Now other additives are used and we call it unleaded.
Ethanol is one of these additives used to increase octane. One method is to add it in the form of MTBE, made by synthesizing ethanol and isobutylene. (But other methods are generally cheaper)
When adding anhydrous ethanol (as in today's ubiquitous E10 gasoline), it raises the octane rating by a couple points.
07-09-2014, 09:53 AM
#29
JK Super Freak
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The link is an Exxon/Mobile page discussing the definition of octane rating and the fact that is has nothing to do with the energy contained in the fuel. I just figured I would include it since one of the major manufacturers of gasoline has on their own web page that higher octane gas than the engine is designed for will not net you any benefit. It would be in their interest to hype the higher octane (more expensive) fuel if they could legally say it would help performance. The science is in the calculation of the rating itself. By definition, it is a measure of the fuel's stability under compression to resist pre-ignition (knocking). It is not a measure of energy contained (heating value). Gasoline has an energy content or Low Heat Value of 20,400 BTU/lb. Ethanol is 12,412 BTU/lb. But Ethanol has a higher octane rating - 99.15 AKI. This is why ethanol is blended with gasoline at up to 10% concentration at most US pumps. It's a cheap and relatively clean way to increase the octane rating of gasoline. We used to add lead to gas to do this, but then we figured out that was pretty bad on the environment and thus all on-highway gasoline is referred to as unleaded. The ethanol blend nets you a lower MPG because it contains less energy, just ask anybody that has used E85 in a flex fuel vehicle. If you want to believe that higher octane fuel gives you better mileage, I won't argue, because you don't understand what octane rating even is. And I'll just watch my stock in oil companies continue to climb.
I'll keep using 87 unless I want extra ping I'll upgrade
07-09-2014, 01:09 PM
#30
JK Junkie
Here's my take... If for whatever reason (carbon build-up, octane less than advertised, etc.) there is short or long term KR (Knock Retard), then increasing the octane will eventually result in less KR (meaning more spark advance). If this is in a zone where a lot of driving is happening, then there's the potential for a slight increase in MPG.