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Discussion Starter · #1 ·
I’m hoping to start a small discussion thread on octane uses and experiences. I have a ’74 CB360 and have been using 93 octane every fill up with no issues. My OEM manual say’s

“91 octane low-leaded gasoline or higher is recommended. If low-leaded gasoline is not available, you may use leaded regular graded gasoline.”

So, when I was filling up at different local gas station the other day, I noticed 100 Octane labeled “For off-road use only”. I was thinking of giving the ‘old CB a taste of the good stuff. Has anyone done this, and if so what was the experience. Or did it harm the bike?
 

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I would have though using lesser octane (and ethanol) would be more detramental to performance....I've never seen or used 110 rated fuel here in Oz.
 

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Discussion Starter · #3 ·
I know you should always use the proper grade for the tune of your engine. So, it says 91 or higher. I just didn"t know if it would run better with 100 or not. My Yamaha YZF450 just loved the high octane, but it was tuned for that. So, I'm thinking of running a tank of 100 in the CB360 for kicks. This is what is up the street http://www.sunocoinc.com/Site/Consumer/ ... o260GT.htm
 

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This is all different depending on what country you are in and how they measure octane. my bike manual calls out for "92" octane. (1971 cb450). All the octane numbers quoted in these old Honda manuals use the RON octane number. (99% sure as this is what most of the world uses, including Japan.) The US pumps are unusual (and Canada, I think) and are all measured in (RON + MON /2) which is also called AKI (Anti-knock Index). AKI is approx 4 to 5 points lower than RON on its own. The fuel is all the same, its just a difference in measuring it and what the label on the pump says.

so, for mine, 92 RON octane ~ 87 (R +M/2) (AKI)

so, should you run higher octane?

generally you only go up in octane from factory recommended if your bike is tuned correctly and is pinging. (burning too soon) or if you have performance modified the engine. i run into a lot of guys who's modern bikes are meant to run regular and they spend all this money putting super or premium unleaded in there thinking it boosts performance, which in effect is delaying your timing as it takes longer to burn and they end up getting LESS performance (and mileage) out of the bike, and the bike runs hotter, as the gas is still burning as the exhaust valves open... just convinced a friend of mine to run regular since that is what his bike wants, and he was very skeptical but has come back stating he can actually feel his bike running better on regular. that is all he has run since.

of course running too low of an octane is bad and can result in pinging and engine damage. if you have upped your compression or advanced your timing etc, you will probably be needing to run a higher octane in order to avoid pinging.

i have not run my 450 long enough to have experimented with upping the octane. but it is stock so i run US 87 and have absolutely no problems with pinging. but not from the cheapy gas stations, have noticed a noticeable difference sticking to chevron or texaco.

i am unsure how the rising ethanol content in US fuels plays into any of this, except some say that it can absorb water, so old gas that has ethanol may not be the advertised octane any longer.... anyone have any info?

thoroughly confused yet? :)
 

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Discussion Starter · #5 ·
I follow you completely, but I was wondering if the ethanol being added now, would it benefit the engine to run a higher octane like Sunoco GT 260 with a RON of 105 and AKI of 100? Also this fuel is still 9% ethanol. I guess I'm just stuck on the gas in '74 is not the same gas in '10, so would we benefit from running a richer octane to counteract the additives that are in the current fuels these days?
 

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delineator said:
i am unsure how the rising ethanol content in US fuels plays into any of this, except some say that it can absorb water, so old gas that has ethanol may not be the advertised octane any longer.... anyone have any info?

thoroughly confused yet? :)
Ethanol (as any form of alcohol) will absorb a certain amount of water that it comes in contact with. It will not suck water out of the air and into your fuel. Nor, as some have claimed, will it suck water through the walls of a steel gas tank. It has been known to dissolve some fuel tank coatings and even some tanks themselves but those problems were mostly addressed a few decades back. Same with some of the "rubber" parts in carburetors. While modern carb kits will work fine with ethanol, some of the NOS stuff may not be compatible.

Personally, I don't use it in engines that are only run occasionally although my skepticism regarding its long term storage characteristics may be outdated.

I've been running it for over 30 years (about as long as it's been available) without any problems but, as usual, to each his own.

++Sorry, that should have been to each his or her own.

+++To its own?
 

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some good info coming out here, everything I wrote is from reading up on the issue and experimenting with modern bikes, I have only had the 450 for 6 months or so and a couple hundred miles, so not much time to get a really good feel for this bike regarding fuel. so the more first hand results people have with their old bikes running different octane's the better. and the pumps are marked "up to 10% ethanol" but I believe the current amounts are below that and the labeling is just so that as they gradually raise the level in the upcoming years they don't need to relabel anything. And it means that can serve you up whatever gas they get their hands on, o%, 1%, 10%

i dont have a good solution, but i always use chevron and try to fill up at the same station every time. i have not had any luck finding any info on stations that do not have ethanol.

not having the label doesn't mean it does not have ethanol, some states don't seem to require it. here is a site, not sure how authentic, as per everything on the net.

http://www.fuel-testers.com/state_guide ... _laws.html

there also appear to be little kits so you could test the fuel quickly, but that just doesn't sound like too much fun...
 

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wonder how accurate this site is? it depends on users posting so would be prone to error or not being up to date, but nice place to start! too bad the only place in seattle is commercial vehicles only...

http://pure-gas.org/index.jsp

and looks like it could get worse...15% anyone?

http://www.komonews.com/news/business/104868109.html

looks like easy to test if there is ethanol or not...

http://www.autofuelstc.com/autofuelstc/ ... ltest.html

got a lead on a local station not on the list above that may have the good stuff. will have to test it.
 

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JT....As an 18 year old chem lab tech I knew that pure ethanol is hygroscopic.....If you buy "200 proof" (Pure) grain alcohol, and open it the proof immediately drops to 199 or less from moisture absorbed from the atmosphere (We had to "correct" our test results based on ambient humidity)..... A 10 or 15% solution is signifigantly less hygroscopic, but to state it does NOT absorb moisture would (I believe) be erroneous... Steve
 

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66Sprint said:
JT....As an 18 year old chem lab tech I knew that pure ethanol is hygroscopic.....If you buy "200 proof" (Pure) grain alcohol, and open it the proof immediately drops to 199 or less from moisture absorbed from the atmosphere (We had to "correct" our test results based on ambient humidity)..... A 10 or 15% solution is signifigantly less hygroscopic, but to state it does NOT absorb moisture would (I believe) be erroneous... Steve
I did not say it does not absorb moisture. I said it won't suck moisture into the tank that isn't already there. As a 30+ year user of the product in everything form 300+ horsepower tractor engines to weedeaters I am well aware that it is not the Holy Grail of anything and I am also aware that most of the horror stories are pure BS.
 

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Discussion Starter · #12 ·
So.....Has any body found or ran 100 (unleaded pump gas) octane? Does anybody know if it will harm :roll: a 36yr old engine?
 

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JT.... I do agree that most "horror" stories about ethanol containing fuels are BS...
{SOME people actually deliberately add alcohols (dry-gas) to their fuel to negate the wintertime in-tank moisture condensation problem.....}

My objections to modern lower-octane fuels is that they don't have the correct additives (like tetra-ethyl lead) to properly cushion the stellite valve seats and edges...Of course, most of my bikes are 60's and early 70's models.... (at the cusp of unleaded).....
 

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It's like discussing which tastes better, Coke or Diet Coke. Which is better, one review says this, another says something different.

I say just try some high-octane gas.
Run your tank down and put 3 or 4 tanks of high octane through it.
If you don't think it runs better, don't use it.
If you think it does run better, then use it.
It won't hurt the engine.
 

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I can't speak for bikes in particular but after reading this from a previous post in this thread:
" i run into a lot of guys who's modern bikes are meant to run regular and they spend all this money putting super or premium unleaded in there thinking it boosts performance, which in effect is delaying your timing as it takes longer to burn and they end up getting LESS performance (and mileage) out of the bike, and the bike runs hotter, as the gas is still burning as the exhaust valves open... just convinced a friend of mine to run regular since that is what his bike wants, and he was very skeptical but has come back stating he can actually feel his bike running better on regular. that is all he has run since."
I was reminded of my extensive note taking on gas mileage in my truck and higher octane fuel.
I got LESS gas mileage with HIGHER octane.
OTOH I had to add octane only for hot weather driving in Mexico on a motor that liked the timing advanced.
I really believe at this point that if it doesn't ping, don't use higher octane gas.

Edy
 

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solarae said:
I got LESS gas mileage with HIGHER octane.
OTOH I had to add octane only for hot weather driving in Mexico on a motor that liked the timing advanced.
I really believe at this point that if it doesn't ping, don't use higher octane gas.

Edy
I know this is an old thread, but...

My experience tends to support these thoughts. I was running regular when I first put the bike on the road and I was getting 60 mpg. Now I am around 55, but I know that I tend to see lower milage with the summer fuel formulations also.

Based on some things I was reading, it sounded like I should be using high test, although I believe that my compression ratio is only at 9.3:1; which would normally only require regular.

On a hot day, I could see the anti-knock compounding come into play and would think high test would help.

I have run about 10 tanks of high octane through the bike (Only 100 miles per tank, wish I had a bigger tank), but I am going to try a few tanks of regular again, since I didn't notice any big changes.
 

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I have also found that i got less with higher octane in MY CAR, it resists knock because it burns slower, if this is not what your engine was designed for, this can make it run worse.

these old bikes are a bit different, and for me, the jury is still out. there are a lot of guys who swear they run better on the higher octane stuff.

of course this is complicated by the ethonal debate as well, as maybe the higher octane fuel has less or more than the lower octane stuff and that is the real reason for the difference, not the actual octane rating..
 

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The Honda RC148 five cylinder 125cc race bike, in 1965, made its usable horsepower in the 20,000 rpm range. They had to run regular grade fuel in it, the high octane wouldn't burn fast enough to keep up with those 20,000 rpm combustion cycles.
 

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The problem is, and explained in an earlier post in this thread, is how octane was measured and sold in the 60's and early 70's, and how it is sold now.

The 2 methods in the 60's was the RON and MON (Research Octane Number, Motor Octane Number).

RON was a higher number, so most gas stations advertised it. The federal government got involved and came up with the Pump Octane Number. This was the (RON + MON)/2.

Today we buy Pump Octane, not research. If your bike calls for 91 Octane (RON), 86 PON is fine. My CB360 actually spells it out, as in 1976 the octane ratings were being adjusted. So regular, at 87 PON is actually a little higher than needed.

This also applies to those older bikes requiring 92 octane (RON). The present day 87 PON is exactly right.

The only bikes that would need higher are ones that have had rebuilds with higher compression resulting (High compression Pistons, Shaved Heads, etc) or ones that are so carboned up that they have pre-ignition (knocking) problems. The right solution to preignition is to de-carbonize the combustion chamber, not use higher octane gas.

Using higher octane in a carbureted engine is waste of money at best. The lower flame front propagation, as stated earlier, results in wasted energy as the extra heat is pushed out the exhaust, and even make the engine run a little hotter.

Properly tuned, a good condition engine only needs the octane that the mfg called for. Higher octane gas is not better gas, not higher quality. In fact, ethanol is actually an octane rating increaser, so more ethanol gives higher octane, but lower energy available.

If you think higher octane on your engine, when not specifically required by the engine, improves performance, you do not understand how an engine works, or how to really improve performance. You are only fooling yourself, and helping Exxon/Mobil stock prices.

Most bikes made in the mid 70's on do not require lead for valve lubrication. The older 4 cycle bikes might. 2 cycle bikes run better on unleaded, as the lead deposits out on plugs and fouls them. If you ever owned an outboard motor in the 60's, you know that "white gas" (which was unleaded, dye is added to gas to ID brand and type) was the right stuff to keep the 2 cycle outboard happy.
 

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here is a question and thought exercise to further this regarding ignition timing.

i have made some gross assumptions here, particularly just pulling timing degrees out of thin air, so treat this train of thought of mine accordingly. :)

lets say we have one of our old bikes and its running on the freeway at 5500 rpm, just cruising along, the centrifical advance (since that is all we have on bikes) is fully advanced, at say 40 degrees BTDC (before top dead center). the fully advanced amount on the bikes is by its nature a compromise, as the centrifical advance unit doesnt know if you are cruising when at 5500 rpm or have the throttle wide open trying to accelerate. my understanding is that for CRUISING, you want MORE timing advance, because the mix is a bit lean and takes longer to burn. Lets say that 45degress was ideal. on the other hand, for POWER, you want less advance, because the mix is richer and burns faster. lets say that 35 degrees is ideal. is this theory correct ? (i am sure the actual numbers are not)

since higher octane fuel burns slower, lets say it takes an additional 5 degrees of rotation to fully burn. this would turn an engine timed at 40 degrees for "ideal burn" at top dead center, into one timed at effectively 35 since now "ideal burn" will be 5 degrees after top dead center.

to me, this means that if timing has NOT been changed on the bike when switching from regular to high octane, that the bike will feel like it has more power, since you are effectively changing the timing to be more power orientated.

what i dont know is how the fuel burn rates of modern ethanol"regular" gas compare to burn rates of "mid 70's" gas. are they different rates even though the effective octane rating is the same? (since octane is a measure of anti-knock ability, not burn rate?)

car ignitions introduced the vacuum advance unit, such that when cruising the intake manifold has a much higher vacuum than with wide open throttle, and that vacuum adds additional advance into the timing for better mileage while cruising, but reduced advance when you jump on the gas. this allowed for different timing at the same RPM dependent on how you are driving. bikes never added this additional complication to my knowledge. modern computerized ignitions do all this and more on both cars and bikes.

as a side note, found quite a few articles about how you need to richen up your mix when using ethanol fuels...
here is one:
http://www.thecarburetorshop.com/Ethanoluse.htm

good info on ignition timing:
http://en.wikipedia.org/wiki/Ignition_timing
 
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