Octane ?
Octane ?
i know what the book and dealer said but i was just wondering what everybody else uses. i been using 93 but heard that since most fuels contain 10% ethonol it boost the octane up. don't know if it is true but tried a few tank full of 89 and my mileage went up. never got more than 35-37 with 93 but been getting 39-41 with 89 and doing the same rideing. strange.
Ultimate HDF Member
Joined: Jun 2009
Posts: 6,932
Likes: 4
From: 46th State, USA
It must be a conspiracy with the oil companies to sell more fuel. Telling everyone they should be using 91 octane when 89 will get them better fuel mileage. I would like to hear an explanation from someone that knows the truth about octane verses fuel mileage. I do know that higher octane fuels have a lower flash point than lower octane.
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Road Captain
Joined: Dec 2009
Posts: 540
Likes: 3
From: Nooga, TN
Octane is a flame retardant and is used where pre-detonation is a problem. Pre-detonation or pinging is a problem in higher compression applications and in high heat applications. As far as BTU's/gallon, energy/gallon, generally the higher the octane rating the lower the BTU's/gallon. In other words there is more energy in a gallon of 80 octane than in a gallon of 93 octane. So you will generally get more miles per gallon with 80 octane than 93 octane, but you risk pre-detonation or pinging. Pre-detonation can be harmful to pistons and other engine components and should generally be avoided.
So running a lower octane rating will most likely increase you gas mileage. Just have to watch out for pinging. Cars have a knock sensor that will retard the timing to prevent pinging so they can handle lower octane, but HD's do not to my knowledge have a knock sensor so they recommend the higher octane to prevent pinging because air cooled motors run kind of hot, especially the rear cylinder.
Have not studied the effect of alcohol on octane rating so I cannot comment on its effects. I will look into it and see.
So running a lower octane rating will most likely increase you gas mileage. Just have to watch out for pinging. Cars have a knock sensor that will retard the timing to prevent pinging so they can handle lower octane, but HD's do not to my knowledge have a knock sensor so they recommend the higher octane to prevent pinging because air cooled motors run kind of hot, especially the rear cylinder.
Have not studied the effect of alcohol on octane rating so I cannot comment on its effects. I will look into it and see.
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Road Captain
Joined: Nov 2009
Posts: 594
Likes: 0
From: Arkansas
I've got one to throw out there, anyone consider a gal of 103 octane to say 3 or 4 gal of 89 to 91 that you can get most anywhere. Would the results be worth it. Found a gas station in the next town over from where I just moved to that sells the 103. Wouldn't do alot of good on a long trip but at least I can do it while ridin locally. Figured it would be better than all the fuel additives I hear some use to raise octane levels..
