Questions about fuel
Bikes call for highest octane pump gas available to you. 93 on the east coast, and 91, 92 was about the best I could find west of the Mississippi. I throw in a little octane boost every 10th tank or so to clean her out a bit.
Cruiser
Joined: Jul 2012
Posts: 247
Likes: 0
From: Southeast Georgia
You should use Premium. If I'm not mistaken the owners manual say at least 91 octane. And really if you figure it up your only saving a $1.50 or so a fill up. So using regular to save money isn't really there. Also if your using your bike as your daily commuter over your car then your still saving money just by riding your bike vs your car. But that's how I look at it.
Advanced
Joined: Aug 2012
Posts: 77
Likes: 0
From: Ohio
Alot of what you will read on this post is incorrect. There has been a misconception of high octane fuels for a very long time. Octane is merely a rating of volatility. The higher the octane the harder it is to burn. This is needed in high compression engines so the fuel doesn't pre-ignite or ping. Most stock engines are rated at 8.9:1 A low compression ratio. Closing in on 10.5 and above I would recommend premium. If you use premium on a low compression engine you are not only wasting money but literally blowing raw fuel out your exhaust. What happens to raw unburnt fuel in a conventional engine....carbon build-up. Not a good thing. Please research this online to validate my point. Been building motors for 25 yrs. Hope I gained some knowledge along the way!
Outstanding HDF Member
Joined: Aug 2012
Posts: 3,217
Likes: 90
From: Detroit
Alot of what you will read on this post is incorrect. There has been a misconception of high octane fuels for a very long time. Octane is merely a rating of volatility. The higher the octane the harder it is to burn. This is needed in high compression engines so the fuel doesn't pre-ignite or ping. Most stock engines are rated at 8.9:1 A low compression ratio. Closing in on 10.5 and above I would recommend premium. If you use premium on a low compression engine you are not only wasting money but literally blowing raw fuel out your exhaust. What happens to raw unburnt fuel in a conventional engine....carbon build-up. Not a good thing. Please research this online to validate my point. Been building motors for 25 yrs. Hope I gained some knowledge along the way!
Octane is not a measure of volatility. It is a measure of combustion stability.
Burn rates only bear a loose relationship to octane, so your remarks about blowing fuel out the exhaust, and carbon buildup, are in error. Premium fuels often have a better detergent additive package, so that's one thing favoring their use if one wants to avoid the buildup of deposits.
There is no ideal, or maximum compression ratio for a fuel octane. It is dependent on things like combustion chamber size, shape, turbulence, spark plug location, heat dissipation, and quench area.
When in doubt, premium fuel is almost never a mistake.
Last edited by Warp Factor; Aug 18, 2012 at 09:33 AM.
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Road Warrior
Joined: Sep 2009
Posts: 1,257
Likes: 2
From: Gastonia, NC
I've run all three grades in my bike. Can't tell a difference. I still get premium most of the time but it doesn't bother me to use another grade.
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Elite HDF Member
Joined: Jul 2010
Posts: 3,830
Likes: 302
From: Lorain Ohio
Same here. On my shovelhead it seems to run cooler (exhaust heat by my legs) on premium, on the evo I didn't notice any difference so I split the difference an run plus.
Extreme HDF Member
Joined: Dec 2007
Posts: 13,402
Likes: 941
From: Illinois
HD recommends 91 but they run fine on 87 as all vehicles sold in the US are required to run on 87 by the EPA. They are even working to make piston aircraft use 87 to eliminate aviation fuel.
If you know not to lug the engine every thing will be okay.
Octane is just a measure of a fuels resistance to ignition and nothing more. I does not make power, it is not premium or better in any way. It is just harder to light up.
It does not "clean up" an engine. In fact the higher octane that you use the less of it will burn during the combustion cycle and will carbon up the motor faster.
I run three bikes with TC96's, one TC103 and one CVO TC110 on 89 octane. Two 1200cc motors also.
Been in 49 states, most of Canada and across every mountain range in the US. Never an issue in 75,000 miles. I do add an oil cooler to those that did not come stock with one and run a 12.1 to 1 fuel programmer.
The engines run cooler and stronger with that set up.
It you have cams and higher compression then yes, higher octane is needed.
But a normal HD Twin Cam runs great on 87 octane and in the mountains 85 is the best to use.
All gas is 115,000 BTU's/gallon no matter what octane it is. Power is from the expansion of hot gasses pushing down on the piston not octane.
12.1 to 1 has been the standard for almost a hundred years because it is the easiest mixture to ignite. The leaner 14.7 to 1 yields the lowest emissions that is why it is used today. Runs the motor much hotter and thus less power.
The lean ratio is also harder to ignite combined with high octane means less of the fuel is burnt and goes out the exhaust.
It's your bike put in whatever you like. But at least know what it is that you are doing in the process.
If you know not to lug the engine every thing will be okay.
Octane is just a measure of a fuels resistance to ignition and nothing more. I does not make power, it is not premium or better in any way. It is just harder to light up.
It does not "clean up" an engine. In fact the higher octane that you use the less of it will burn during the combustion cycle and will carbon up the motor faster.
I run three bikes with TC96's, one TC103 and one CVO TC110 on 89 octane. Two 1200cc motors also.
Been in 49 states, most of Canada and across every mountain range in the US. Never an issue in 75,000 miles. I do add an oil cooler to those that did not come stock with one and run a 12.1 to 1 fuel programmer.
The engines run cooler and stronger with that set up.
It you have cams and higher compression then yes, higher octane is needed.
But a normal HD Twin Cam runs great on 87 octane and in the mountains 85 is the best to use.
All gas is 115,000 BTU's/gallon no matter what octane it is. Power is from the expansion of hot gasses pushing down on the piston not octane.
12.1 to 1 has been the standard for almost a hundred years because it is the easiest mixture to ignite. The leaner 14.7 to 1 yields the lowest emissions that is why it is used today. Runs the motor much hotter and thus less power.
The lean ratio is also harder to ignite combined with high octane means less of the fuel is burnt and goes out the exhaust.
It's your bike put in whatever you like. But at least know what it is that you are doing in the process.