100 octane
Cruiser
Joined: Sep 2006
Posts: 121
Likes: 0
From: Hershey, PA
RE: 100 octane
I have had over 30 cars in my life and currently have a Corvette in addition to my Street Bob as my toys.
I am also active on a variety of forums and without a doubt ocatane is brought up and posts are made as to the value of high octane fuel and how performance is enhanced in every forum. This is all based on a misunderstanding of what octane means. High octane fuels are not more powerful, they are more resistant to compression detonation in opoosition to the ability to burn more easily (referred to as combustion).
Fuels with higher octane ratings "explode" less easily--in higher compression engines they do not tend to predetonation when the compression increases. Lower octane rating fuels will explode more easily and so are more suited to lower compression engines.
The best fuel to use in any particular engine is the octane at which the engine runs without predetonation. Using an octane rating that is higher than necessary provides no advantage in terms of power; this has been proven time and time again with dyno testing.
However using an octane rating lower than optimum will result in predetonation (knock) and can damage the engine.
You can "tune" and modify engines to prevent the knock and also to gain minor performance gains from higher octane fuels, but in general it is an expensive and wasteful means to gain performance.
Some of this misunderstanding comes from the roots of high performance sports cars and motorcycles that have one version for racing and are essentially "detuned" for street use. People believe that the race vehicles simply are using higher octane and so put that in their engines to gain the racing performance.
Use the fuel that you are most comfortable with, but the likelihood is that the motors you refer to would run just as efficiently (and definitely more cheaply) with a fuel of lower octane rating.
I am also active on a variety of forums and without a doubt ocatane is brought up and posts are made as to the value of high octane fuel and how performance is enhanced in every forum. This is all based on a misunderstanding of what octane means. High octane fuels are not more powerful, they are more resistant to compression detonation in opoosition to the ability to burn more easily (referred to as combustion).
Fuels with higher octane ratings "explode" less easily--in higher compression engines they do not tend to predetonation when the compression increases. Lower octane rating fuels will explode more easily and so are more suited to lower compression engines.
The best fuel to use in any particular engine is the octane at which the engine runs without predetonation. Using an octane rating that is higher than necessary provides no advantage in terms of power; this has been proven time and time again with dyno testing.
However using an octane rating lower than optimum will result in predetonation (knock) and can damage the engine.
You can "tune" and modify engines to prevent the knock and also to gain minor performance gains from higher octane fuels, but in general it is an expensive and wasteful means to gain performance.
Some of this misunderstanding comes from the roots of high performance sports cars and motorcycles that have one version for racing and are essentially "detuned" for street use. People believe that the race vehicles simply are using higher octane and so put that in their engines to gain the racing performance.
Use the fuel that you are most comfortable with, but the likelihood is that the motors you refer to would run just as efficiently (and definitely more cheaply) with a fuel of lower octane rating.
Intermediate
Joined: Nov 2007
Posts: 28
Likes: 0
From:
RE: 100 octane
I'm no expert, so I won't say to definately take my advice, but I have always heard to use the recommended octane for your motor and as long as it isn't knocking, using anything more would be a waste of money and contribute to more carbon build-up.
Advanced
Joined: Feb 2006
Posts: 93
Likes: 0
From: Southeastern Idaho
RE: 100 octane
Agree with Cigarman....and to add in that octane requirements are a function of the compression that you can build in a given engine....which changes with combustion chamber size and or the dome of the piston...but also greatly with elevation above sea level....so a 12:5:1 compression ratioengine may require 100 octane at sea level however at 7000 ft above sea level you typically will get no detonation or ping with 88 octane gas.......never checkedmystbob but my ktm dirt bike with a manufacture rating of 11:5:1 compression ratiowith a compression gauge installed will crank out about 137 lbs at about 1700 ft of elevation and here in New Mexico at 7200 ft it will only crank out about 108 lbs......my 2 cents.
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Road Master
Joined: May 2006
Posts: 941
Likes: 27
From:
RE: 100 octane
ORIGINAL: jhmp
Will it hurt or help?
My 40year old machines love it. Just wondering if it will damage these new motors?
Will it hurt or help?
My 40year old machines love it. Just wondering if it will damage these new motors?
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Road Warrior
Joined: Dec 2007
Posts: 1,437
Likes: 0
From:
RE: 100 octane
ORIGINAL: jhmp
Will it hurt or help?
My 40year old machines love it. Just wondering if it will damage these new motors?
Will it hurt or help?
My 40year old machines love it. Just wondering if it will damage these new motors?
Either the engine is set up to take advantage of it, and it will run with more power and smoother (and you can actually ruin it using lower octane fuel) or it isn't, in which case it's just a waste of money, but your engine will guzzle it like lower octane without any problem.
You only must be aware you are wasting money.
"Octane" only function is to prevent detonation.
Low compression, low angle of ignition engines don't need it, but if you put it in them, it won't do any harm whatsoever.
How a certain octane rating is obtained is a different issue whatsoever.
READ CAREFULLY!
Lead was an octane enhancer in older fuel. Removing the lead, it actually made the modern leadless fuel lower octane. So, many older engines, set to burn high octane fuel, seem to like premium leadless fuel. No pinging, they run smoother etc...
But the lead in older fuel served also a lubricant purpose for the valve seats. Older engines may have or not have hardened valve guides. If they do have them, then you've got no problem. If they don't, you put leadless, and in some thousand miles you'll blow them. EVEN if the engine seems to like 100 octane! [:-]
This is true of ANY leadless fuel!
In this case, in fact, the problem is not the octane rating, but the lack of lead!
Road Master
Joined: Nov 2006
Posts: 1,164
Likes: 401
From: Port Coquitlam B.C.
RE: 100 octane
cigarman is right on the money. Further to his comments, the higher the octane the slower the burn of the fuel. Meaning if you are running a higher octane then recommended you will see a decrease in power unless you advance the timing of the engine to compensate for the longer burn time.
