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Octane ratings, separated as off topic from a previous post

8K views 43 replies 19 participants last post by  D.T. 
#1 ·
It doesn't matter. Most people use 87 and have no problems. It's the old fallacious pot leads to heroin argument.
87 octane won't cause a problem, but too high an octane can cause a problem with valves. If the fuel burns too slow and builds up carbon the valves can start to leak. Burning oil can cause a similar issue. Especially on higher mileage vehicles 50,000+ miles. The OP's post seems like the problem came on too quick for either of these to be the case.
 
#2 ·
#3 ·
I read that article and as far as I can see, it explains it the way that I have understood it since I was a Construction Mechanic in the SeaBees. The arguments about complete burn and explaining that a high RPM Pro Stock engine needs to burn quickly are misleading. Of course a Pro Stock needs the fuel to burn quickly and the conditions of its combustion is quite different then a stock motorcycle. Put 87 octane in that Pro Stock and it will ignite quicker, and burn quicker then the fuel used in their example. Thus the 118 octane fuel will ignite slower and burn slower then the 87 octane fuel. I guarantee it.

Octane is the only number we really have to go by. What I was taught was that you should use the lowest octane fuel that you can without inducing detonation. Using a higher octane may cause your combustion chamber and valves to get carbon buildup. It really depends on those other factors as described in your linked article. Different brands of fuel may be quite different in their burn rate after ignition.

I know of people that have used higher octane ratings without any problems and I now of people that have had to have the heads removed and valves redone because of it. I even have one friend that twice had to have their Jetta's head removed. They then believed me about the fuel they were using and didn't have a problem after that.

I personally don't know of anyone that has had a carbon buildup problem using the correct octane.
 
#5 ·
Since different brands come from the same refineries, I would go on to say the differences in the same octane ratings of different brands is in the additive packages. The only advantage I can see in higher octane fuels is if the additive package is better. I like to use the lowest octane fuel available that doesn't cause pinging but has a good additive package to keep things clean. Since six top auto makers established a standard for additive packages in all grades seen at Top Tier Gasoline , I like to stick to those brands. Since I've never had any of my vehicles ping, I use the lowest octane available in those brands including 85 in higher elevations. I have never had an engine problem or a bad fuel problem.
 
#6 ·
Since six top auto makers established a standard for additive packages in all grades seen at Top Tier Gasoline
I hadn't seen this before. I'll have to make sure the places I get gas are on this list.

My 81 GS1100E is the only bike that I have had that was fussy about octane and brands. My user manual for it recommends trying different brands of fuel when experiencing pinging using 89 octane.
 
#8 ·
Just a note that the USA/Canada use a different octane rating (MON) to most of the rest of the world which use RON - so the numbers are not the same..

For example, unleaded here is 91 RON, premium is 95 or 98 RON (there are two grades of premium).
 
#9 ·
Close. North America uses (R+M)/2 so a North American 87 is close to the rest of the world's 91.
 
#12 ·
Do you really want to know a lot about gasoline? Here's Chevron's "Motor Gasolines Technical Review." It is not self-serving, and it has more than any of us thought we wanted to know about gasoline. It starts off, "In May 1876,
Nicolaus Otto built the first practical four-stroke-cycle internal combustion engine powered by a liquid fuel." and goes on to cover every base after that.
http://www.chevronwithtechron.com/products/documents/69083_motorgas_tech_review.pdf

By the way, we all know the name of a diesel engine, named after Rudolph Diesel and technically called a Diesel cycle engine. Did anyone know that our usual four strokes-per-power-cycle gasoline engines are actually Otto cycle engines?
 
#41 ·
Do you really want to know a lot about gasoline? Here's Chevron's "Motor Gasolines Technical Review." It is not self-serving, and it has more than any of us thought we wanted to know about gasoline. It starts off, "In May 1876,
Nicolaus Otto built the first practical four-stroke-cycle internal combustion engine powered by a liquid fuel." and goes on to cover every base after that.
http://www.chevronwithtechron.com/products/documents/69083_motorgas_tech_review.pdf

By the way, we all know the name of a diesel engine, named after Rudolph Diesel and technically called a Diesel cycle engine. Did anyone know that our usual four strokes-per-power-cycle gasoline engines are actually Otto cycle engines?
Upgraded link for the Chevron document: https://www.chevron.com/-/media/chevron/operations/documents/motor-gas-tech-review.pdf
 
#13 ·
The recommended grade is in the owners manual or usually posted on a sticker near the fuel cap. Why not just believe the manufacturer?
My 800ST is supposed to use Premium but the owners manual says you can use regular with a drop in performance. I've yet to experience a drop in performance or mpg.
Most of us have no problem with the 650 and regular.
I think the fuel of choice falls into the same category of personal preference as OIL, TIRES and WINDCREENS, oh my!
 
#14 ·
Octane, again

Octane is the resistance to pre-igniting due to radiated heat in the combustion chamber. Flame travel speed is more a function of gas turbulence (swirl) in the combustion chamber than octane rating. Some relatively high-compression engines get by with regular gas because of superior combustion chamber and intake tract design. Our Suzukis are not included in that group.
 
#15 ·
Some relatively high-compression engines get by with regular gas because of superior combustion chamber and intake tract design. Our Suzukis are not included in that group.
Meaning of course that they are not high compression so there's no benefit to higher octane regardless of combustion chamber design. Save your money for a cold beer after your ride!


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#16 ·
11.5:1 on the Wee, 11.3:1 on the Vee and 11.2:1 on the Glee aren't exactly low compression engines. My 1975 BMW R90S was 9.5:1 and it required premium. It's more the combustion chamber and air flow characteristics on the Stroms that permit regular fuel than the compression ratio.
 
#19 ·
I never had a problem with 85 where it was available. It makes sense to me that an engine will have a lower combustion chamber pressure at altitude, the equivalent of a lower compression engine at sea level.
 
#20 ·
octane mpg compar-o

the proof of how good the pudding is, is in the taste. IOW's, one must do a compar-o to find out which octane 87-89-93, is best for their bike and riding style. thats what i did. i found from my experience that the higher the octane i used, the better my mpg was. with 93 octane giving me the best average mpg. see fuelly link for more info..
 
#21 ·
the proof of how good the pudding is, is in the taste. IOW's, one must do a compar-o to find out which octane 87-89-93, is best for their bike and riding style. thats what i did. i found from my experience that the higher the octane i used, the better my mpg was. with 93 octane giving me the best average mpg. see fuelly link for more info..
I don't know if you really have enough data there to draw strong conclusions about the octane. If you graph it you will see that your mileage varies enough from tank to tank that it might be hard to make a conclusion based on the fuel type. (I graphed yours for fun.) In my case running regular fuel (for the most part) over about 155,000 miles on my two Stroms the mileage variation from tank to tank is similar to yours. (643 fillups on the 2006 and 151 on the 2012)

..Tom
 
#22 ·
In the best of cases, premium may provide 1% better mileage unless regular has ethanol and premium does not. Then it can be as much as 3%. That isn't nearly enough to offset the cost difference.
 
#23 ·
I run 85 Octane in all my vehicles, as I live at 5000 ft...except for a turbocharged Escape, where I stick with the manufacturer recommended 87 minimum. I track every tankful of every vehicle I've ever owned for mpg. I found NO mpg correlation between 85 or 87 or 88 or 89 Octanes. What I did find was weather-related coorelation, as well as the obvious idle-times and load-related coorelations. Plus, how do you know the pumps are giving you accurate delivery volume measurements? I don't believe they are calibrated that well from station to station....or, even if using the same pump, can't the delivery calibration drift? Obviously, my experiences really don't mean anything, as the variables are too hard to control. Similarly, one other person's experiences is just another anecdotal scrap of evidence, which doesn't really have significant meaning. Especially when people find they get a very small difference in mpg, I don't place any value in their report. You need a calibrated volume of fuel, on a prescribed course, with the same vehicle, under the same driving conditions (weather, wind, barometric pressure), using the same tires (pre-heated, so, the first lap doesn't start on cold tires), at the same temperatures, with the same driver...and switch back and forth between different fuels, before I'd believe any small changes in efficiency. Then, you'd have to change the driver, and get the same small difference in efficiency. Only then would I believe a 1, 2, or 3% difference. And, that's just for that particular driving course and speeds. Super-or Turbo-charged vehicles are able to get pretty darn good efficiency on very low octane fuels, as long as the boost is kept minimal. But, when that boost comes on, in order to take full advantage of the boost, many of these systems REQUIRE higher and higher Octane levels to avoid pre-detonation. So, again, it depends upon the load requirements as to whether there is better performance, or, better efficiency, or both...or neither...depending upon blah-blah-blah.

However, can't significant detonation easily be heard in smaller engines with stock mufflers? I know in engines I've had in the past, not only could I hear it, but, I could feel the power output wane. If that is true, and I'm not positive that it is true, as long as you don't hear it/feel it, your Octane level isn't too low for those specific driving conditions.
 
#25 ·
What I did find was weather-related coorelation, as well as the obvious idle-times and load-related coorelations.
Gasoline has two different standards in the northern part of the US and for you's guys in Canada (I don't know about the south), there's a winter and a summer vapor pressure standard that changes about this time of year. It's not your bike that varies with temperatures, it's the gas. I work in a refinery. Winter gas will give you lower mpg, them's the facts.
 
#26 ·
Summer blend fuel, lessened warm up times, softer wheel bearing grease, and less dense air to punch through all contribute to better warm weather fuel economy.
 
#29 ·
on a recent 87 vs 93 octane mpg compar-o that i did, i got 2.9 better mpg using regular automotive grade fuel with the highest AKI rating. :yesnod:
http://www.stromtrooper.com/746492-post1.html
Assuming gas at $3.50 per gallon and getting a nominal 50 mpg, you can't pay more than about $.20 per gallon extra for the higher octane without losing money. So if this mileage increase is real you might break even if you're a very careful shopper. But why bother?

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#28 · (Edited)
please, explain to us how your "test" was performed under a constant so as to be exactly scientific? and what was your two average MPGs? what percentage of increased fuel economy with "93"? how much money did you save with your increased MPG with premium fuel vs regular over the course of your tank?

i can ride my bike to work for a week using regular fuel and using premium. i bet i can get 10mpg better with regular fuel. ;)

edit: going through your fuelly i only see you using 93? your graph mimics that of my 91 Civic Si, in that both averages drop in the colder months and are best when it's warmer. i don't see any comparison on 87 vs 93 though on your actual account??

edit: found them in July 2012. they seem extremely erradic, though, and not very consistent? you averaged from as low as 40 mpg to as high as 51 on just 87 alone..

edit again cause i don't want to make multiple replies and am slightly bored at work; your rolling average right now is 45.7. let's round to 46. so you say you get 2.9mpg better with premium, putting your regular fuel MPG at an average of 43. currently cost of premium is 3.91 at the closest station to me, and 3.51 for regular. cost per mile for premium is: 3.91/46= .085 per mile. regular is: 3.51/43= .081. you seem to be wasting .004 cents per mile. added up to over 100k miles that is $400. so generally not a HUGE cost increase over the course of mile after mile, but if you changed your riding habits along with using regular i would assume that you could reduce your costs much more.

2.9/45= about 6% fuel savings using premium but still not enough to make a difference in cost..
 
#32 ·
LOL guys, sounds like earthmuffin blew his engine up using regular automotive fuel with the lowest AKI rating. i do believe that it would have been cheaper to use regluar fuel with the highest AKI rating. http://www.stromtrooper.com/1150641-post1.html
That's wild conjecture with no basis in fact. There is zero evidence higher AKI fuel would have made any difference. He doesn't even know why the engine failed yet. The only basis you have to make that comment is it feeds your agenda, an unreasonable love of premium fuel. Wera688 has over 275,000 miles on his Vee using only 87 octane fuels.
 
#33 ·
When I feel the urge to splurge on fuel I don't buy octane. Instead I go to a Phillips 66 station about 5 miles from home that sells pure gas, no alcohol, even in 87 octane. I run that in all of our mowers and power equipment. I put it in the bikes during the more dormant winter months. Phillips has the added advantage of using a Top Tier
additive package. Thanks for the Top Tier tip GW.
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#38 ·
There is not one clue that detonation was the problem. It is absurd to intimate a wee would have destroyed an engine using regular and would have been okay with premium. All your link shows is detonation and pre-ignition are harmful.

I could post a link to how low oil pressure destroys engines but that has no more validity to the subject than your link.
 
#40 ·
That post says he doesn't yet know the problem.
 
#43 ·
After a summer of a diet of pretty much straight premium "Rez" gas I decided to give my Oldstrom (03 DL1000) a treat and filled up with ESSO supreme plus 93 octane, I have to say it has never run better!! BTW most premium grade fuel is "E" free here in Bantario, if gas contains it they have to put a label on the pump.
 
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