89 octane
#12
04-22-2014, 12:27 PM
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Normally, a 9.5 to 1 motor (10 to 1 on water cooled rushmores) wants 86/87 octane gas, so not sure why harley is specifying 91 octane in the owners manual for the 103's. Gas suppliers mix local supplies based on altitude and expected temperatures, so right now the middle grades is always 89 in my area, and that's what I would use if you want to follow the suggested octane recommended by manufacturer. But if a middle grade weren't available, I would go low before I would go high with 93 octane, which is formulated for an 11 to 1 motor.
Dealers sold 93 octane as "premium" for so long, that some ill-informed folks will continue to use it believing that their ride deserves the best. But the plain fact is, that all three commonly sold mixes contain the same package of ingredients, and the octane number is just a measure of how fast the gas ignites, with lower octanes igniting faster. A gas that ignites too quickly will knock in a high compression motor, and a gas that ignites too slowly will not burn completely in a lower compression motor.
So, the combination of compression and ignition advance determines what will work best, not marketing.
Dealers sold 93 octane as "premium" for so long, that some ill-informed folks will continue to use it believing that their ride deserves the best. But the plain fact is, that all three commonly sold mixes contain the same package of ingredients, and the octane number is just a measure of how fast the gas ignites, with lower octanes igniting faster. A gas that ignites too quickly will knock in a high compression motor, and a gas that ignites too slowly will not burn completely in a lower compression motor.
So, the combination of compression and ignition advance determines what will work best, not marketing.
#14
04-22-2014, 06:20 PM
We are at 4500 feet above sea level so we can run 89 octane with or with out ethanol. I
don't do it all the time, and less so in the Summer when we go weeks above 90 degrees
or low hundreds. With this Bike I ride solo all the time, the Wife's arthritis dose not permit
to ride anymore. (:>) I am not worried about pinging so far so good.
don't do it all the time, and less so in the Summer when we go weeks above 90 degrees
or low hundreds. With this Bike I ride solo all the time, the Wife's arthritis dose not permit
to ride anymore. (:>) I am not worried about pinging so far so good.
Last edited by OldPhat; 04-22-2014 at 06:23 PM.
#15
04-22-2014, 06:42 PM
I put pure gas in my 08 for a while couple years ago. After just 1 tank it began starting very hard but ok once started. Changed plugs same thing. Decided to go back to 93 ethanol and within a tank and a half it ran like it used to.
Few guys from the club also started using it and reported hard starts, missing, light smoking so now all of us just use the regular ethanol stuff with 0 problems.
Few guys from the club also started using it and reported hard starts, missing, light smoking so now all of us just use the regular ethanol stuff with 0 problems.
#16
04-23-2014, 08:42 AM
I ran a variety of fuel, 87, 89, 90, 91, and 92 octane in my 2000 Ultra (yes it was an EFI). Never noticed any difference no matter what. I tended to run 90 or higher when it was over 80 degrees out. I was told at one point that hihger octane burns "cooler" and that is why HD recommends it in the air cooled engines. Not sure if that is true or not. But in the cooler weather, I ran 87 a lot with no pinging or any other problems.
With my 2014, I am sticking with the high octane for a while. No need to challange the motorcycle gods with a new engine!
With my 2014, I am sticking with the high octane for a while. No need to challange the motorcycle gods with a new engine!
#17
04-23-2014, 09:55 AM
On a fully liquid cooled engine I'd agree with you, but on an air cooled engine like the Harley's have the engine has a tendency to detonate on lower octane. I cheaped out and put regular in my RK once in the middle of the summer, the bike just pinged away until I got 91 back in it.
#18
04-23-2014, 03:03 PM
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