So  I traded bikes with my roomate for the day about two weeks ago under the promise that we would fill each others bike up. (He rides an '07 ZX6R) not knowing my bike takes 87, he put 91 like his bike uses. He tells me this and I'm like no biggie, I'll just fill it up with 87 next time.

When I ride my bike though, it feels great very responsive and torquey, especially on the highway. I decided to try one more full tank of 91 just to see how it goes. Bike has felt very good with only me having to use slightly more choke upon starting it up but I'm still using no choke in less than a minute, usually before I'm even geared up and ready to ride. Now today I filled it up with 87 and figured my gas mileage when using 91. It was 56.6mpg, about 2mpg better than I usually get using 87.

This really suprised me. I expected it to be around 52-53ish since I've actually been riding my bike a bit harder. Now it has been very hot here in OK, 95-100+*F everyday, and I hear higher octane is better for hotter weather.

Now two questions. . .

Has anybody else experienced this?

What do I risk by continuing to run 91?

Bike is an '09 with 5800 mi.

you mostly risk spending more money on gas 
Over the past few months I also experienced increase in my mileage. I keep refuelling at the same 2 stations and I always buy 87... I can't precisely explain the increase. I GUESS:
- better carb synchronization
- gentler driving
- less choke for start ups

In other words I don't think you should assume that your mileage increased just yet. If it is consistent for few more fuel ups then maybe. Right now I would be very skeptical about it.

I just filled up Suki with 91 too and noticed that shes not quite as cold blooded, running alittle smoother and is withstanding the heat alittle better. im an automotive mech so my training all wants to scream  but my gut, my butt, and previous experience tell me that occacionally it does make a difference. higher octane fuel burns slower and and slightly cooler. so it may be bandaiding my tight valves, lean running, and unbalanced Suki.  soooooo..... there no clear cut answer but ill see how she performs on  and off with i fix these problems one by one.

IMHO opinion, i have found fuel economy impacted more by environmental factors than by octane ratings. With more than 42,000 miles in the last 3.5 years (and I have tracked MPG on EVERY tank of gas I've put into my '07), I find air temperature to be the most influential factor (outside of a heavy throttle hand).

I consistently average about 56-58 in the winter and 62-64 in the summer. Why?  Two factors: 1) Warmup time. I don't think I need to discuss this. 2) Air density: this means drag. Winter air is heavier, drier and more dense than summer air. The warmer the air, the more moisture it can hold, and moisture (H20) weighs less than the O2 it replaces, making the air lighter and less dense. This means less drag in the summer air and better gas mileage. It's no coincidence my best gas mileage occurs during the hottest part of the year!

My $0.02

Quote from: MVent03 on August 27, 2011, 11:08:23 AM
So  I traded bikes with my roomate for the day about two weeks ago under the promise that we would fill each others bike up. (He rides an '07 ZX6R) not knowing my bike takes 87, he put 91 like his bike uses. He tells me this and I'm like no biggie, I'll just fill it up with 87 next time.

When I ride my bike though, it feels great very responsive and torquey, especially on the highway. I decided to try one more full tank of 91 just to see how it goes. Bike has felt very good with only me having to use slightly more choke upon starting it up but I'm still using no choke in less than a minute, usually before I'm even geared up and ready to ride. Now today I filled it up with 87 and figured my gas mileage when using 91. It was 56.6mpg, about 2mpg better than I usually get using 87.

This really suprised me. I expected it to be around 52-53ish since I've actually been riding my bike a bit harder. Now it has been very hot here in OK, 95-100+*F everyday, and I hear higher octane is better for hotter weather.

Now two questions. . .

Has anybody else experienced this?

What do I risk by continuing to run 91?

Bike is an '09 with 5800 mi.

There is a thread on oil.......same applies for octane, or gas brand...

Search the internet and find about all the myths.........

People will swear on their mother about the benefits of higher octane...but without proof....the only way to prove any of the claims would be with a "Blind taste test"........that is have many riders test out bikes without knowing what gas was in them, then even telling them they had high octane when they didn't as a "control".......of course the many many variables would all have to be controlled.

"feel"..."perfromance"......mileage....are based on so many factors.....like temperature, humidity, driving style, etc..


Higher octane won't hurt the machine.....it's all about getting the money out of your wallet and into somebody elses.

Cookie

I was gonna say "don't tell Cookie  " but... too late 

Yes, generally speaking, you are far more likely to get a change in mileage due to other things besides Octane, on a GS500 - octane is NOT an Energy Rating but rather an Anti Knock rating (higher compression engines have a tendency to autodetonate like a Diesel engine, so this tendency is reduced by having gas with high antiknock, higher octane).

However, *I* found the lower octane from one particular brand gives poorer performance.

Where we are there are two refineries - BP and Caltex (and they have a supply pipe linking to each other's refinery so if one is low on raw crude they can get some from the other when a ship comes in). All fuel in our area comes from either those two, regardless of the Brand. Where we are, 7/11 gas Stations get their fuel from Shell. Shell has no refinery, they are just a tank farm and commission Caltex to create fuel according to Their (Shell's) specs.

*I* have found, using the lower Octane from 7/11 (Shell) I get less mileage. BUT, using the lower, mid or high octane from BP I get the same mileage. The bike also Sounds better - sounds like it is running better - on the BP. So for me, the brand made a difference. My car also runs poorer on Shell than BP. Something in the Shell mix doesn't agree with my two Suzukis.

Barring that, like I said, there is no Difference in performance between the various BP octane fuels.

OH... one thing I was told by Caltex is, they have an additive in their higher octane (higher than standard) to help keep fuel injectors clean. I could surmise that some performance change Might be seen as a result of such an additive keeping the jets cleaner. But that's only a theory.

Michael

Quote from: mister on August 27, 2011, 12:54:32 PM
I was gonna say "don't tell Cookie  " but... too late 

Yes, generally speaking, you are far more likely to get a change in mileage due to other things besides Octane, on a GS500 - octane is NOT an Energy Rating but rather an Anti Knock rating (higher compression engines have a tendency to autodetonate like a Diesel engine, so this tendency is reduced by having gas with high antiknock, higher octane).

However, *I* found the lower octane from one particular brand gives poorer performance.

Where we are there are two refineries - BP and Caltex (and they have a supply pipe linking to each other's refinery so if one is low on raw crude they can get some from the other when a ship comes in). All fuel in our area comes from either those two, regardless of the Brand. Where we are, 7/11 gas Stations get their fuel from Shell. Shell has no refinery, they are just a tank farm and commission Caltex to create fuel according to Their (Shell's) specs.

*I* have found, using the lower Octane from 7/11 (Shell) I get less mileage. BUT, using the lower, mid or high octane from BP I get the same mileage. The bike also Sounds better - sounds like it is running better - on the BP. So for me, the brand made a difference. My car also runs poorer on Shell than BP. Something in the Shell mix doesn't agree with my two Suzukis.

Barring that, like I said, there is no Difference in performance between the various BP octane fuels.

OH... one thing I was told by Caltex is, they have an additive in their higher octane (higher than standard) to help keep fuel injectors clean. I could surmise that some performance change Might be seen as a result of such an additive keeping the jets cleaner. But that's only a theory.

Michael

LOL.....hey...whatever makes you happy! 

Just to show the variables....I use gas from the same station around the corner from my house...I always use "regular".....My mileage varies from 60 to 70 MPG.....lowest I ever got was 59 and tops was 72.........

But that represents a 16% swing due to factors other than the gas!!!


In terms of cost.....hight test is only about 2 to 3% more expensive around here...so why not go for it!? 

Cookie

IIRC, don't some stations keep ethanol out of their high grade gas? A mixture of 100% gasoline will get you more power and mileage than a 90/10% mix of gas and ethanol- regardless of knock rating.

actually most company's have more ethanol in there premium then in there regular, ethanol is a octane booster... in pure form its 110 octane so if you mix it in with lower octane gas you get premium!

Quote from: Big Rich on August 27, 2011, 02:04:40 PM
IIRC, don't some stations keep ethanol out of their high grade gas? A mixture of 100% gasoline will get you more power and mileage than a 90/10% mix of gas and ethanol- regardless of knock rating.

Ethanol is a bad idea and will ruin the gas mileage......there are some staions with "pure gas" but not in my state.....

I can get 100 actane "straight" gas (with lead) where I work at the airport....lots of guys use it in Two Stroke engines....they say the ethanol gas will not run right..

But at $6.00 a gallon...I'll have to pass on that..

Cookie

I agree with you Cookie. I meant to specify that if the high octane gas the OP got was ethanol free, that would explain the power and mileage gains.

Either that, or there are some problems with pre-ignition in their engine and the anti knock qualities of high octane gas are a band aid.

To clarify, I only use 100% gasoline. No ethanol.

I was surprised when I did the math and figured my mileage. I did it twice to make sure. If I'm not going to ruin or prematurely wear anything, I'd like to continue the experiment. The difference between filling up with 87 vs. 91 is about $1.10 per tank. I think I can swing that. I'm still saving money over driving my car.

I also get my gas from Shell usually. 7-11 if I'm in need and can't find a Shell. I'm not real brand loyal, just no ethanol.

Quote from: MVent03 on August 27, 2011, 05:51:56 PM
If I'm not going to ruin or prematurely wear anything, I'd like to continue the experiment.

Go for it. If there was any damage to be expected, the European guys would mention that. I run mine with 95, sometimes 98. No problem at all (except for the costs)! 

I always run on 98 no matter the brand but I try to stick with v power (shell) for my bike and car.

in the haynes manual 89 t0 08 models recomended minimum91 oct .I myself run 98 octane BP  and average 69 to 70 mpg my bike has timing advanced large jets bigger airfilter . no trouble with starting   .and more lively performance .Spark plugs have done 6000 miles and look good for another 6000  .with a compression ratio of 9.0 to 1 it is on the edge to be running anything lower than 91 octane .98 octane is cleaner burning because the lower the octane the more oil is in the fuel hence less performance .Any fuel above this would not be an advantage unless you increased the compressin ratio to take advantage of it ,and why would you want to with such a great engine.

Quote from: MVent03 on August 27, 2011, 05:51:56 PM
To clarify, I only use 100% gasoline. No ethanol.

I was surprised when I did the math and figured my mileage. I did it twice to make sure. If I'm not going to ruin or prematurely wear anything, I'd like to continue the experiment. The difference between filling up with 87 vs. 91 is about $1.10 per tank. I think I can swing that. I'm still saving money over driving my car.

I also get my gas from Shell usually. 7-11 if I'm in need and can't find a Shell. I'm not real brand loyal, just no ethanol.

Most "experts" say that entanol in gas is likely to damage motorcycle engines over time.    Pure gas will not cause these damages.  It has to do with water retention of ethanol.


Cookie

Quote from: twinrat on August 28, 2011, 12:46:14 AM
in the haynes manual 89 t0 08 models recomended minimum91 oct .I myself run 98 octane BP  and average 69 to 70 mpg my bike has timing advanced large jets bigger airfilter . no trouble with starting   .and more lively performance .Spark plugs have done 6000 miles and look good for another 6000  .with a compression ratio of 9.0 to 1 it is on the edge to be running anything lower than 91 octane .98 octane is cleaner burning because the lower the octane the more oil is in the fuel hence less performance .Any fuel above this would not be an advantage unless you increased the compressin ratio to take advantage of it ,and why would you want to with such a great engine.

Compression ratio is not the only factor to consider when talking octane required......

Old airplane engines had relatively low compression ration...but really big cylinders...lots of piston area..need high octane due to area.....motorcycles have usually small pistons...can go higher compression ratio without higher octane necessary....it all about "knock" (preignition)

I hate to start an arguement...but "cleaner burning" doesn't enter into it....

Basically if you have "knock" you need higher octane or engine modification or tuning....If you don't have "knock" you don't need higher octane.   If higher octane means no ethanol, go for it...

Higher octane will yeild more power, ONLY IF the engine is designed and tuned for that.....there is no more power in the fuel....it just means the engine can be tuned to be more effecient....like higher compression, advanced timing...."stock" gs will not benefit..........

When you read the manuals...you have to be careful of which "octan rating system" is being referred to..........there are two basic systems which yield different octane rating for the same gas.....in USA they calcualte both ways and average them together to give the number you see at the pump..........

Cookie

From Wiki:

Research Octane Number (RON)The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.

Motor Octane Number (MON)There is another type of octane rating, called Motor Octane Number (MON), or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load, as it is determined at 900 rpm engine speed, instead of the 600 rpm for RON.[2][3] MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON, however there is no direct link between RON and MON. Normally, fuel specifications require both a minimum RON and a minimum MON.[citation needed]

Anti-Knock Index (AKI)In most countries, including Australia and all of those in Europe, the "headline" octane rating shown on the pump is the RON, but in Canada, the United States and some other countries, like Brazil, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI, and often written on pumps as (R+M)/2). It may also sometimes be called the Pump Octane Number (PON).

Difference between RON and AKI Because of the 8 to 10 point difference noted above, the octane rating shown in the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel. See the table in the following section for a comparison.

I generally ride in places where 115 octane fuel is available. I stick to the lowest grade I can find. Pure gas is better than ethanol gas, IMO.

Quote from: twinrat on August 28, 2011, 12:46:14 AM
in the haynes manual 89 t0 08 models recomended minimum91 oct .I myself run 98 octane BP  and average 69 to 70 mpg my bike has timing advanced large jets bigger airfilter . no trouble with starting   .and more lively performance .Spark plugs have done 6000 miles and look good for another 6000  .with a compression ratio of 9.0 to 1 it is on the edge to be running anything lower than 91 octane .98 octane is cleaner burning because the lower the octane the more oil is in the fuel hence less performance .Any fuel above this would not be an advantage unless you increased the compressin ratio to take advantage of it ,and why would you want to with such a great engine.

Hmmm, on Flick it is plainly stated 87 minimum why is haynes different? BTW Flick hates the pricey stuff he's cheap like his owner LOL!

Mary