If you are using 91, and didn't care to get it running the best it can run, you can lean it back via jetting to indeed get better gas mileage. 91 will knock and ping at a much later stage than 87 and as such can be run leaner cos lean = detonation ... however 91 = less likely detonation ...
Cool.
Buddha.

The 98 you're filling up is probably RON octane rating. It's about the equivalent of 91 octane fuel in the states. 91 RON octane rating fuel is, based on a quick search, generally not available in the UK... But if it were, it would be about the equivalent of US 89 octane fuel (RON+MON/2) Check your manual for what rating method is specified; it's very possible that if you have a UK localized manual that it's specifying the equivalent of US Regular unleaded fuel.

What about shell v power or bp ulitmate? Both are 98 ron fuels sold in many different countries surely it's the same formulation. I mean even the F1 cars use v power. So at least v power is the same no matter where.

Quote from: aussiegs on August 31, 2011, 02:55:43 PM
What about shell v power or bp ulitmate? Both are 98 ron fuels sold in many different countries surely it's the same formulation. I mean even the F1 cars use v power. So at least v power is the same no matter where.

What's the difference between 95 kilometres and 59 miles?

MON+RON/2 and RON are different ways of rating gasoline. The same fuel will have different octane ratings on each scale, despite being the same. Generally, the mapping is 87=91, 89=95, 91=98.

My bad sorry always wondered why the US had 89 and 91. I thought it meant u guys were running a lower octane fuel than the rest of us.

All consumer-grade gasoline has the same basic ingredients in the soup, but the additives vary widely depending on where it is sold. In the US, methanol and methanol blends are used widely thoughout the midwest part of the country, but I haven't seen it here in southern California yet.

Gas is gas, but only to a point; environmental regulations in different parts of the US dictate changes to the final product, among other reasons. People in the US snow belt get a different blend during the winter than we get here, where "winter" means the temps don't usually go much higher than about ~75F, which is ~25C... They have to start COLD engines with thick oil; if the temps go much below ~45F here (~7C) during a winter night, my girlfriend wants an extra blanket on the bed...

I read somewhere, that if you use an octane rating significantly higher than what is recommended, it burns hotter, which tends to be bad for the spark plugs or something.

I dont know about gas mileage, but i do notice that the bike seems a bit smoother and happier on 93 octane here in MA.

Quote from: The Buddha on August 31, 2011, 12:05:41 PM
If you are using 91, and didn't care to get it running the best it can run, you can lean it back via jetting to indeed get better gas mileage. 91 will knock and ping at a much later stage than 87 and as such can be run leaner cos lean = detonation ... however 91 = less likely detonation ...
Cool.
Buddha.

Probably a different topic but what would you do to get it running the best it can?

Are you just referencing the timing advance and re-jetting?

So let me tell you s short story...
I am coming back home from school few days ago and I notice that my bike feels really smooth and edgy like it had a bit more power. I am thinking "this is nice" and I play with throttle a bit, speed up slow down and try to come up with a reason why it feels better.
Then I realized that I fuelled it up with Premium gas because the gas station was out of regular due to Hurricane Irene. I keep going home, flick of a wrist 2nd, 3rd gear, 70mph, I am thinking: shoot I need to slow down, and I do.
I kept enjoying the ride and then I suddenly recalled this thread about Regular vs Premium gas. I was thinking to myself that there must be something to this Premium gas myth, even though I have done a research many times and knew better.
And then I recalled one more thing... It was my car that I filled with premium and not my bike...

So what I am trying to say is that unless you can precisely measure power output and smoothness of the ride, it is safe to assume that both grades of gasoline give you the same results. It is all in our heads how we perceive our bikes on a given day.

Slightly different example: sometimes I love the sound of my pipe and think it's not loud and sometimes when I have a bad day it annoys me and I keep shifting at 5K just to keep it quiet...

Kinda like a GS with an exhaust "feels" faster just cause it's louder   

-Jessie

Quote from: mass-hole on September 01, 2011, 11:35:44 AM
I dont know about gas mileage, but i do notice that the bike seems a bit smoother and happier on 93 octane here in MA.

I notice differences from station to station.

In practice, if you have detonation or pre-ignition issues, even relatively mild ones, premium will make the bike run better. A good spark plug inspection can help identify any such issues. Otherwise, I'd expect the bike to run better and make more power on regular.

Quote from: mass-hole on September 01, 2011, 11:35:44 AM
I dont know about gas mileage, but i do notice that the bike seems a bit smoother and happier on 93 octane here in MA.

I hear this type of claim again and again..Hey, you can't argue with success, right?  Well I can!

The trouble is that concepts like "smoothness" and   "happiness"  are really subjective.   It's the percemption is reality kind of thing....

The only way I would be convinced, is if we got say 20 GS500 bikes and riders...and  did a "mythbusters" type of blind test......giving riders tanks of gas, without them knowing what kind of gas......and then seeing they can identify what type of gas purely by the "feel" or the sound, or the happiness....we could also do mileage tests.......it would be quite and undertaking however....filling and emptying tanks......checking all the other variables too...

Cookie

Quote from: kml.krk on September 01, 2011, 12:41:31 PM
So let me tell you s short story...
I am coming back home from school few days ago and I notice that my bike feels really smooth and edgy like it had a bit more power. I am thinking "this is nice" and I play with throttle a bit, speed up slow down and try to come up with a reason why it feels better.
Then I realized that I fuelled it up with Premium gas because the gas station was out of regular due to Hurricane Irene. I keep going home, flick of a wrist 2nd, 3rd gear, 70mph, I am thinking: shoot I need to slow down, and I do.
I kept enjoying the ride and then I suddenly recalled this thread about Regular vs Premium gas. I was thinking to myself that there must be something to this Premium gas myth, even though I have done a research many times and knew better.
And then I recalled one more thing... It was my car that I filled with premium and not my bike...

So what I am trying to say is that unless you can precisely measure power output and smoothness of the ride, it is safe to assume that both grades of gasoline give you the same results. It is all in our heads how we perceive our bikes on a given day.

Slightly different example: sometimes I love the sound of my pipe and think it's not loud and sometimes when I have a bad day it annoys me and I keep shifting at 5K just to keep it quiet...

Perception vs reality..

Cookie

Quote from: burning1 on September 01, 2011, 03:22:59 PM

Quote from: mass-hole on September 01, 2011, 11:35:44 AM
I dont know about gas mileage, but i do notice that the bike seems a bit smoother and happier on 93 octane here in MA.

I notice differences from station to station.

In practice, if you have detonation or pre-ignition issues, even relatively mild ones, premium will make the bike run better. A good spark plug inspection can help identify any such issues. Otherwise, I'd expect the bike to run better and make more power on regular.

How do you "see" detonation by looking at the spark plug???  I could "see" mixture....or "see" oil fouling.....or "see" heat range....but I though you "hear" detonation......

A motor designed for regular, with no mechanical problems, will most likely run just the same on regualr and on premium.......premium will just waste money.....

Somtimes an engine designed for regular gets "carboned up" which causes an actual increase in compression due to the build up....then it may get knock...and may not knock on premium......but I consider carboned up to be a mechanical problem...



Cookie

Quote from: twocool on September 01, 2011, 08:08:16 PM

How do you "see" detonation by looking at the spark plug???  I could "see" mixture....or "see" oil fouling.....or "see" heat range....but I though you "hear" detonation......

You do "feel" detonation while riding but if ignored it will eventually physically damage the spark plug.

-Jessie

It's amazing how different people focus on different opinions about octane...

twocool basically has it...if your engine is rated for regular fuel (Euro-Aussie ~ 91, North America ~ 87) puting higher octane in the tank won't hurt the engine, but won't help either...yes, you may notice a difference but as twocool stated:

Quote from: twocool on September 01, 2011, 08:08:16 PM
Somtimes an engine designed for regular gets "carboned up" which causes an actual increase in compression due to the build up....then it may get knock...and may not knock on premium......but I consider carboned up to be a mechanical problem...



Cookie

Usually it isn't an increase in compression that causes detonation or "knock"...it's the carbon build-up retaining heat and causing detonation...but same result...you get "knock" and using a higher octane fuel will "mask" the problem...

(I think mister suggested this earlier in the thread...about the higher octane masking the problem)

Octane itself is a rating of the fuels ability to resist detonation...basically it is a rating of what temperature will autoignite the fuel...if heat due to higher compression, carbon deposits, impurities, etc are causing knock, a higher octane rated fuel will make the engine run smoother (since it won't be firing before top dead center) and make it seem to have more power, when really it is the same power but running better due to not igniting prematurely...

As for the different stations giving you different results, it's because the different refineries have different additives in their fuel mixtures...some are better for colder climates, some have more cleaning agents...some have more impurities in them...and that is usually what leaves the deposits in the engine that makes you want to use premium fuels...

There is nothing "hi-tech" about the GS, it is a basic commuter set up bike and requires only regular fuel...if you find it runs better on higher octane fuel, run it...just know that your engine could use an overhaul to go back to running regular...probably just easier and cheaper to run the premium...

Anyway, I know there is no one answer that will convince everyone so continue with the debate...it comes up atleast once a year anyway...

Later.