OCtane ???
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Joined: Feb 2013
Posts: 56
Likes: 2
From: Winter Haven Florida
OCtane ???
I have read about this all over the Net ! but this is the first time I needed to know what is going on... My 2011 1200L has 9.7 to 1 Compression ! Why do I need to Run 91 Octane Fuel?? My other bikes had 10 to 1 and never a problem with Knocking caused by The Fuel..Also a Caddy. but the caddy had knock sensors that retarded the timing to prevent Knocking. Which also reduced Power and Gas mileage.. The way it is Explained to me is the Higher the Octane the Slower the burn.. So if you use 91 Octane in a engine that don't need it, you are dumping Raw and half burned fuel out the exhaust.. You can add a 1/2 bottle of STP Fuel injector cleaner every 5 tanks to get the same benefits of the additives added to 91 Octane.. So what is the Deal.. ??? by the Way am I going to prison for not running HD Dunlop Tires And Harley Oils.. I will Run Mobil 1 . They had to revive me at the Dealer after I read the Service Prices and fainted.. It is so aimed at the Yuppies that don't ride anyway. My 2011 Had less than 5000 miles.. SAD !!
For the oil I also use Mobil1 V-Twin. I like it a lot. For the trans oil I do buy the harley brand, whatever its called..
As for the gas, the manual recommends 91. Where I live we only have 87, 89, 93. So I just use the 93. What do you have against the higher octane fuel? Is it the price? At a full tank you're probably looking at a matter of 20-30 cents.
As for the gas, the manual recommends 91. Where I live we only have 87, 89, 93. So I just use the 93. What do you have against the higher octane fuel? Is it the price? At a full tank you're probably looking at a matter of 20-30 cents.
Road Captain
Joined: Dec 2012
Posts: 566
Likes: 4
From: Milton, PA
Lower octane fuels in a engine designed with a high compression ratio can cause pre-ignition which can cause all sorts of problems, including the audible knock.
Worth it to save a buck? Not in my book.
I've changed my own oil in every car, truck, and motorcycle I've ever owned. My Harley will be no different. Mobil 1 is good enough for my car. The V twin Mobil will certainly do the trick for my bike.
Worth it to save a buck? Not in my book.
I've changed my own oil in every car, truck, and motorcycle I've ever owned. My Harley will be no different. Mobil 1 is good enough for my car. The V twin Mobil will certainly do the trick for my bike.
Stellar HDF Member
Joined: Aug 2009
Posts: 3,212
Likes: 212
There are a million other factors that dictate the required octane level for no knock operation including but not limited to: valve configuration, ignition timing, chamber design, spark plug location, thermal capacitance of the material, valve timing, dynamic compression ratio, squish, tumble, swirl, AFR and more.
Novice
Joined: Sep 2012
Posts: 24
Likes: 0
From: San Antonio, TX
The higher the octane, the higher the autoignition temperature.
The higher the compression, the more heat generated in the combustion chamber.
The more heat in the combustion chamber requires a fuel that won't ignite due to the higher temps as a result of that compression.
The higher the compression, the more heat generated in the combustion chamber.
The more heat in the combustion chamber requires a fuel that won't ignite due to the higher temps as a result of that compression.
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