100 Octane VP Racing Fuel
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Joined: Jan 2011
Posts: 54
Likes: 0
From: Southern California
100 Octane VP Racing Fuel
So , yesterday I pulled into a 76 gas station here in San Bernardino , Ca to top off my fuel for my twin cam 88 fxdl and there it was .....Gas here in so cal for premium 91 octane is $3.50 a gallon , but lo and behold this station had the 100 octane available with the push of a button for $6.99 a gallon . My first impulse was to put in a gallon to liven it up a bit , but , walking in to the counter I had to wonder , how much hotter would this fuel really make it run , not to mention it being twice as expensive . The freeway heading to the desert and Colorado river jet boating , is where this station is at , this gas is for those guys , right ? Anyway , I just put in 91 octane to be safe , but , let me get some opinions from you all , would it make it run a lot hotter , would it do any damage to my stock motor , would it run any better to even justify ?
Road Captain
Joined: Sep 2009
Posts: 556
Likes: 1
From: Long Island, NY
It wouldn't make the bike run any better, in fact it may make it run worse. Octane higher than what is needed is a waste of money and won't burn right. Remember, the higher the octane, the harder it is to ignite.
Road Master
Joined: Aug 2010
Posts: 1,039
Likes: 0
From: Central FL
Alot of newer cars actually have it in their manuals to NOT use anything but Low Grade fuel.
Ultimate HDF Member
Joined: Mar 2008
Posts: 7,604
Likes: 38
From: Landrum, SC , elevation 986'
The higher octane fuel is for higher compression motors. Unless you have a high compression motor its a waste to run it.
Compression Octane Number Brake Thermal Efficiency
Ratio Requirement ( Full Throttle )
5:1 72 -
6:1 81 25 %
7:1 87 28 %
8:1 92 30 %
9:1 96 32 %
10:1 100 33 %
11:1 104 34 %
12:1 108 35 %
Compression Octane Number Brake Thermal Efficiency
Ratio Requirement ( Full Throttle )
5:1 72 -
6:1 81 25 %
7:1 87 28 %
8:1 92 30 %
9:1 96 32 %
10:1 100 33 %
11:1 104 34 %
12:1 108 35 %
Elite HDF Member
Joined: Feb 2008
Posts: 3,817
Likes: 2
From: Novi MI
Octane is an anti-knock compound. Nothing more. So if your engine runs on 91 octane you're wasting your money on anything higher.
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Seasoned HDF Member
Joined: Oct 2007
Posts: 8,852
Likes: 2,494
From: Decatur, Alabama
My ironhead loves high octane fuel (keep in mind it's 35 years old). When I ran 100LL aviation fuel in it, it was much smoother and ran better. When I shut it down it would stop immediately with no dieseling like a Ford Pinto. There was also no knock.
I can tell a difference in the Road King when I have used low octane fuel. It runs much rougher. Runs fine on 93 octane. I would not want to run anything higher than that in it.
I can tell a difference in the Road King when I have used low octane fuel. It runs much rougher. Runs fine on 93 octane. I would not want to run anything higher than that in it.
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