Which Octane?

[drtbkeryder4]

Hi, this is kinda a silly question but anways here goes. I've just bought a 1999 Suzuki Bandit GSF250 and before it arrives I'd like to know what kinda fuel these bikes were made to run on, 91 or 96? I know it should run fine on any of these but which would be the best to use for everyday sorta use. Cheers guys

[zadok]

This subject seems to come up every now and then. From everything I've read about it etc; it is a waste of time putting any more than the regular in it, unless the manufacture specifies a higher octane must be used.

[drtbkeryder4]

ok then, cheers mate. 91 shall do the trick then

[onearmedbandit]

91 will be fine.

[Disco Dan]

This subject seems to come up every now and then. From everything I've read about it etc; it is a waste of time putting any more than the regular in it, unless the manufacture specifies a higher octane must be used.

..would this apply to most/all bikes then? (excluding, high performace bikes etc)

just plop 91, in it.

[Steam]

So when I'm riding my crappy old GN around, is it just my imagination that when I run it on 98 it has slightly better pickup than 91? I coulda sworn it was better, amazing what imagination can do.

[Static]

yea iv been curious bout this i have a cbr250r and was wonderin should i b usin 91 or higher?

[sugilite]

I just won the 6 round Actrix Senior Post Classic championship on my ZXR750 running on 91. :yes:

[gijoe1313]

dizzam, I was told by the previous owner of my ride that premium was what he put into it, good enuff for him, good enuff for me! So... waste of time putting in the more expensive stuff? :mellow:

[Crazy Steve]

91 will be fine.

Dnt think soooo..

96 on these GSF250...

Crazy Steve..

[onearmedbandit]

Dnt think soooo..

96 on these GSF250...

Crazy Steve..

Many would disagree however. Is that from personal experience CS? I know guys who run 91 in their sports bikes with no dramas. Not me however, my bike prefers 96.

[Karma]

91 my ass... sluggish like a bastard on 91, won't touch the stuff... 95 is ok, but I'll run it on 98 whenever possible.

Seriously, run it on a tank of 98, then try stepping down to 91, it's just painful.

[James Deuce]

(excluding, high performace bikes etc)


You'd have to have a pretty radically worked high performance bike to need more than 91. The only bike I've owned that specified 95 Octane was my TRX, but then it depends on what Octane rating you are talking about RON or DIN?

[Bonez]

I just won the 6 round Actrix Senior Post Classic championship on my ZXR750 running on 91. :yes:Congrats. How's the race prep on your new toy coming along?

[lukelin250]

91 is rocket fuel for any 250 yay yeahhh :scooter:

[drtbkeryder4]

well cheers guys, it seems its split like 60/40 to 91. I think that should do for what ill be doin eg. puttering around town. Cheers

[sugilite]

Congrats. How's the race prep on your new toy coming along?

Cheers Bonez.
The 10 is coming along nicely.
An akrapovic exhaust system has arrived and that with some good tyres should see me having some fun!

[Karma]

You'd have to have a pretty radically worked high performance bike to need more than 91. The only bike I've owned that specified 95 Octane was my TRX, but then it depends on what Octane rating you are talking about RON or DIN?

Yeh, but need isn't always it though is it. Technically all your body needs is bread and water, but fucked if I'd live like that.

All I know is that on my 400 it runs much sweeter on 96/98 than it does on 91, but each to their own.

[James Deuce]

Yeh, but need isn't always it though is it. Technically all your body needs is bread and water, but fucked if I'd live like that.

No it doesn't and yes you would be fucked. Worse than if you lived on the "Supersize Me" diet.


All I know is that on my 400 it runs much sweeter on 96/98 than it does on 91, but each to their own.

I have a theory about that. It goes like this: 95/98 octane fuel costs more so my Internal combustion engine MUST run better on it.

[Fryin Finn]

You'd have to have a pretty radically worked high performance bike to need more than 91. The only bike I've owned that specified 95 Octane was my TRX, but then it depends on what Octane rating you are talking about RON or DIN?
Hot Damm Jim - I only ever ran 91 in my TRX didn't seem to harm it at all - d'you think i was missing a few GG's. Got over 60mpg from it too.

[James Deuce]

Hot Damm Jim - I only ever ran 91 in my TRX didn't seem to harm it at all - d'you think i was missing a few GG's. Got over 60mpg from it too.

To bo honest I put 91 in mine most of the time too. It specified 91 - didn't say I used it :). Mind you the sticker was in Japanese, so I'm assuming the 96 in amongst the pictograms was referring to fuel.

[toymachine]

My Bandit always ran on 91 and I continued to do so until last fillup where I went 95...

Can't say I really noticed much other then it's perhaps a tad smoother and doesn't seem to get a strange rattle after long periods with VVT on...

[Karma]

No it doesn't and yes you would be fucked. Worse than if you lived on the "Supersize Me" diet.

That guys a pussy mate, I've been living on that diet for like 5 years.


I have a theory about that. It goes like this: 95/98 octane fuel costs more so my Internal combustion engine MUST run better on it.

I'm well aware of the placebo effect, and I'm not disputing that it may be partially responsible for the results I've seen, but I'm also aware that the bike runs smoother since I started using it, and that's good enough for me.

If you're a little short on cash, or just simply prefer 91, I'm sure there's no ill effects on your bike from doing so. I'm not gonna say that bikes can't use 91, just saying that both myself and my bike prefer 96/98.

[Maverick]

I normally use 98 in my bandit 250,
I find that If I use 95 I sometimes get a weak spot in my power about 8,000 rpm, doesnt happen on 98. Based on that I havent tried 91. Only use 95 when I have to, Shell 95 seems particularly bad but then thats the one I mainly had to use so cant really say for others,

Mav :rockon:

[The Stranger]

Do you know what pinging is or what it sounds like?
If you are getting any pinging then consider a higher octane, if not use 91 (or whatever the manufacturer specifies)

In the GSXR I use the highest octane available around town because I do get a little pinging now and then with 91. On the open road I use 91. There is no appreciable power increase with the high octane, well none that I can discern.

In the Blackbird it was cheaper to run on higher octane fuel and had a noticeable power increase. The Blackbirds have a knock sensor and retard the timing if knock is detected. Not sure, but I believe this may have impacted on the results with the blackbird.

[James Deuce]

Shell 95 seems particularly bad but then thats the one I mainly had to use so cant really say for others,

Mav :rockon:

It is. Mileage is terrible too. 10-12% less than other distributors. Blame ethanol

[MSTRS]

CaN, the term you refer to is 'pinking', I believe. Normally caused by too-advanced timing on low(er) octane fuel, when the engine is under load. The answer is either - increase the fuel octane, retard the timing, or best of all, never let the engine labour.
As an aside, I used 91/95/98 at various times in the 1100 - it run fine on any of them, but best on 98. Have only used 95 in the 750 so can't comment there.

[The_Dover]

The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.

The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.

I think that's a fairly good explanation of it. Why the fuck would your engine run better on a fuel that is designed to ignite at a higher compression ratio?

It's all in the mind. If your engine is not a high comp performance motor then why waste your money on higher octane fuel than you need??

It runs better, bollocks, that's like saying you get pissed quicker on poofy boutiqe beers with a lower alcohol content cos they taste nice and cost more..."it's the designer bubbles..."

load of old toss.

[onearmedbandit]

Well said Dover.

[Steam]

The official workshop manual for my mighty GN250 says "Gasoline used should be graded 85-95 octane or higher."
So now I'm confused. It doesn't make any difference to me on my whimpy GN I suppose, but it is interesting.

[The Stranger]

CaN, the term you refer to is 'pinking', I believe. Normally caused by too-advanced timing on low(er) octane fuel, when the engine is under load. The answer is either - increase the fuel octane, retard the timing, or best of all, never let the engine labour.
As an aside, I used 91/95/98 at various times in the 1100 - it run fine on any of them, but best on 98. Have only used 95 in the 750 so can't comment there.

Why do you call it pinking?
It is commonly referred to either way, just like duct tape (the silver tape, once used to secure air DUCTS to plenums) and for some strange reason duck tape which is I suppose used to package ducks for transport.
I choose to use pinging as I feel it more accurately describes the sound made when pinging (or pinking if you like) takes place. I mean we all know what a ping sounds like, but only a few or us know what a pink sounds like.

[Steam]

Anyone got a link to a sound file of pinking / pinging?
I'd be interested to hear.

[The_Dover]

it's not a fucking performance issue for christs sake, it's a pre-ignition issue (which may lead to poorer performance, granted).

higher octane fuels require higher compression cos they BURN SLOWER.

[The Stranger]

It's all in the mind. If your engine is not a high comp performance motor then why waste your money on higher octane fuel than you need??

It runs better, bollocks, that's like saying you get pissed quicker on poofy boutiqe beers with a lower alcohol content cos they taste nice and cost more..."it's the designer bubbles..."

load of old toss.

Your comparrison is a bit lame there. Where you to equate low alcohol with low octane and high alcohol with high octane you will see immediately why you should be drinking high octane fuel.

The blackbird is (well was) cheaper to run on 95 and cheaper again to run on 98, so that is why I would "waste" my money. It got better fuel milage on the 95 and 98 in over 40 consecutive tests to the point that dollars expended per 100km were less on the higher octane fuels. Not saying all bikes will produce the same result at all, but maybe it is worth a try.

[The Stranger]

Anyone got a link to a sound file of pinking / pinging?
I'd be interested to hear.

No, but imagine an aluminum piston slapping rapidly in a steel cylinder.

[The_Dover]

No, my comparison was not comparing low alcohol to low octane at all (in fact the reverse). It was an analogy of the misconception that if it costs more it must be better.

As you said yourself the 'bird had a knock sensor, i'd surmise that it adjusted the timing and fuelling accordingly, maybe not.

The people I am getting at are the ones that have no understanding of pre-ignition (pinging, pinking, knocking, burping, farting whatever you call it) and what the octane ratings of fuels actual pertain to.

High Octane is not a measure of the calorific value of a fuel. The only thing which affects a fuels power output is the calorific value of the mixture, not it's octane rating.

[The Stranger]

No, my comparison was not comparing low alcohol to low octane at all (in fact the reverse). It was an analogy of the misconception that if it costs more it must be better.

As you said yourself the 'bird had a knock sensor, i'd surmise that it adjusted the timing and fuelling accordingly, maybe not.

The people I am getting at are the ones that have no understanding of pre-ignition (pinging, pinking, knocking, burping, farting whatever you call it) and what the octane ratings of fuels actual pertain to.

High Octane is not a measure of the calorific value of a fuel. The only thing which affects a fuels power output is the calorific value of the mixture, not it's octane rating.

In one of the previous threads on this subject someone posted a file (pdf I think) which showed that higher octane fuels can and do have a higher calorific value (though if I recall correctly it wasn't termed calorific) will try and find it after work for you.

[Delirium]

I think that's a fairly good explanation of it. Why the fuck would your engine run better on a fuel that is designed to ignite at a higher compression ratio?

It's all in the mind. If your engine is not a high comp performance motor then why waste your money on higher octane fuel than you need??

It runs better, bollocks, that's like saying you get pissed quicker on poofy boutiqe beers with a lower alcohol content cos they taste nice and cost more..."it's the designer bubbles..."

load of old toss.
that quote pretty much sums it up. it is the high compression engines that are 'high preformance' that require high octane feul.
also, if you observe the majority of the quotes on this thread then you'll see that the people that say their bike runs better on 95/98 actually have high performance bikes.

[The Stranger]

that quote pretty much sums it up. it is the high compression engines that are 'high preformance' that require high octane feul.
also, if you observe the majority of the quotes on this thread then you'll see that the people that say their bike runs better on 95/98 actually have high performance bikes.

Exactly.
Take say a 250 pulling 33hp and compare it to say a late model cage engine of say 6 litre pulling 400hp.
The 250 is a high performance engine, not far off of the same HP per litre as the blackbird.

[The_Dover]

so how do they run better?

would someone like to dyno their bike on a tank of 91, tank of 95 and tank of 98??

[gijoe1313]

:gob: You mean after all this time, there are still some issues which are a black art? I woulda thunk that this sort of thing would have been cleared up by now! :shit: Surprising to know that this technical boffin thing is still keeping riders in the dark!

Damn, should really read that English Translation manual of my bike :doh: Ah well, guess I'll still stick 98 into my tank...why? Because I can :yes:

[The Stranger]

so how do they run better?

would someone like to dyno their bike on a tank of 91, tank of 95 and tank of 98??

Just spoke to Toby (mechanic and I believe the shop foreman) at Henderson Motorcycles to see if I can get the GSXR on the dyno for this.

I asked him what he thought the outcome of a dyno run would be. He commented that he doubted there would be much difference at top end if any. He said he felt you may notice it in low to mid range.

This pretty well lines up with my experience on the Blackbird.

He also has a K3 GSXR 1000 and commented that he experiences pinging around town on 91 also and 98 eliminated this, but otherwise couldn't feel any difference in power on the GSXR.

Got to talk to Adam (at Henderson Motorcycles) to see if I can get it on the dyno though. I will try and go see him on Saturday and see if he will indulge me.

["D" FZ1]

91 is fine for most smaller bikes.

[Jeaves]

This thread is getting interesting...so will add a little now and some more afterwards.

Ponder this question for now.

How does your bike know what fuel you are putting in / running.

[The_Dover]

fuckin hell CaN, I'm not arguing about it for the gixxer you tit, suzuki state 95 RON or above for it.

it's a high compression, performance engine.

IS A GN250?? OR A GSF250? I'm talking about people who run 98 and say it makes a performance difference to their shit heap 250 or toyota corolla.

[Motu]

Why do you call it pinking?
.

That's the English term,and us old farts always called it that.More of a pink,or plink sound than ping,which sort of implies ringing,which is not the case...pink is a dead sound....follow?

Back in the days when we actually tuned engines,final timing adjustment was done listening to pinking,just a tad of pinking pulling from 20mph in top gear.

[MSTRS]

That's the English term,and us old farts always called it that.More of a pink,or plink sound than ping,which sort of implies ringing,which is not the case...pink is a dead sound....follow?

Back in the days when we actually tuned engines,final timing adjustment was done listening to pinking,just a tad of pinking pulling from 20mph in top gear.

WE gotta stick together against the yunguns eh??

[The Stranger]

...pink is a dead sound....follow?



Get with the times old man.
Pink don't sound too bad at all really, she looks ok for that matter too.

[The_Dover]

i think she's getting fat.

lay of the high octane diet Pink you porker.

[sugilite]

My experience is that if you run a motor on a higher octane gas than it is designed/tuned you will lose low end power. When I was racing the ZX9R Superbike, It was a running very high compression. When I ran it on straight race gas there was a noticeable loss of low end power, so I started running 70% race gas 30% 91 and hello low end power again, thanks to 91's faster burn time. It was even more noticeable when I ran straight av gas in my KX500 motard bike, as in where the hell has the low end power gone? No amount of jetting changes seemed to recover it. Thank goodness the old 70/30 ratio worked on that too.

I noticed the 10 was designed to run on 90 octane or higher, I could not tell the difference between 91 and 98, though now we run a race ECU, I run 98 all the time now.
I tried 91, 95, 96 and 98 in the 750 and settled on 91, and as mentioned won the championship running 91.
Believe me when I say I rung that poor bikes neck and I would have noticed any slight horsepower increase that higher octane "may" have given me.

Long story short, just run the bloody things on what the manufacture specifies, no point going higher unless you tune for it.:scooter:

BTW, the "race" gas you get from gas stations near the race tracks is just stale aviation fuel the airports have dumped, thus the octane level will never be consistent.

[vtec]

I just won the Streetstock racing Series on my CBR250RR running 91 octane. The bike is designed for it, and despite being a screamin' 250, it's compression ratio isn't insanely high. Another point to consider, for the high revving bikes. A faster burn (lower octane) should mean that you get more power... You want to run the lowest octane you can without having to retard your engine to avoid pinking, as that will usually give you the most power... Just check the manufacturer's specifications.

When I used to run 98, it didn't run as well lower in the rev range, used to miss a bit... it seemed to make the bike run a little rich... Botany Honda mechanic recommended that I only run it on '91.

Each bike is different though... all depends on design. I know that my Honda Prelude needs 98, as it can develop a knock if run on 91.

[Sketchy_Racer]

Yep what Vtec and Sugilte said.

I was Came second in Streetstock (behind Vtec) On my KR150.

I ran it on 91, as it was cheaper. and 96,98 made no difference.

Most streetbikes are tuned for crap fuel, so there is no point wasting money on expensive fuel if it does nothing for the bike.

[xsive-rider]

91 my ass... sluggish like a bastard on 91, won't touch the stuff... 95 is ok, but I'll run it on 98 whenever possible.

Seriously, run it on a tank of 98, then try stepping down to 91, it's just painful.

i reckon!
you may as well put water in there than use that 91 shit, good for jappa cages.

[onearmedbandit]

Despite what 3 people who race have said, along with all the other info provided?

[Jantar]

I have kept a careful record of fuel use on my DL1000 ever since new. I started doing it as part of Jim2's fuel comparisom re the new Shell fuel. What I have found is that there is not a noticeable power difference between 91 and 95 in any brand of fuel, but I am getting close to 8% better fuel mileage from 95 than from 91 octane. That is considerably better than the price difference.

I can't say that this would be the same on any other bike, so all I can recommend is that each rider keep their own records and see if there is any difference for their own bike.

[Grahameeboy]

Get with the times old man.
Pink don't sound too bad at all really, she looks ok for that matter too.

We get pinking in Devonport!!

[Bonez]

Many would disagree however. Is that from personal experience CS? I know guys who run 91 in their sports bikes with no dramas. Not me however, my bike prefers 96.My old GSX750EX hates 91 too, pinks like hell. Reading the old write ups indicates this was a common thing with them. Runs sweet on 95. But I feel with a timing tweek will sort out the pinking to run on 91.

[The Stranger]

Ok, ok, I know the subject is done to death.
But here I go again anyway.

As I commented, the gains (torque and fuel economy) I experienced were in low to mid range. Somehow I suspect that if you are winning races you are not spending a lot of time in that area. I am sure I will be corrected if I am wrong there.

As a matter of interest, did you try runing 98 and advancing the timing a couple of degrees. If you are after more performance I would think this would be worth a try.

I aren't trying to say that all vehicles will benefit from higher octane, indeed my SS commodore runs better on 91 right through the rev range. But I am trying to say it is worth evaluating with an open mind, and you should not write it off just because of the higher initial purchase price.

[sugilite]

As I commented, the gains (torque and fuel economy) I experienced were in low to mid range. Somehow I suspect that if you are winning races you are not spending a lot of time in that area. I am sure I will be corrected if I am wrong there.

I'm not sure you are are addressing directly, but as I'm one of the racers I'll reply :yes:

I do run in the lower rev ranges on some corners and I also tend to be a gear higher than most through the corners (must be something to do with my ride style) so yeah, I really do notice any drops in power in the lower ranges.
Most of my testing was done on my private test track that has everything from tightening radius hairpins to 2 km straights. :Punk:

I did make timing adjustments for my KX500, but had to as I had to run the 70/30 av gas/91 mixture so it would not grenade on long straights found on road race tracks....

As mentioned in an earlier post, unless you tune for it, stick to the recommendations of the manufacturer.:done:

[sugilite]

I finally tracked down a article i did for supermoto.co.nz
My 500 had blown up and i went to the master of octane info, Robert Taylor.
heres the article...

The other Weekend my KX500 came to a grinding halt whilst racing at Manfield. After a top end tear down, the electrosil was found to have flaked off the barrel. Not good as I had not long just got it back from the platers. Turns out it was due to detonation. I was running BP Ultimate 98, so I was surprised to find that it had been detonating that badly. A respected motorcycle figure did some research on BP98 by contacting BP themselves. Guess what, you can forget NZ petrol octane ratings as they are quite misleading. Read on....

Here are some of the details supplied to me on the matter. (In italics)
The specs for BP98 are alarming. I don't know whether you are aware of same but all "pump" petrols (98 is a 'pump' petrol as such) have their octane ratings listed as the RON or research octane method. This is a little misleading and is not the information that racers really require.
Looking at the attached spec sheet the MON or motor octane rating of this fuel is in fact only 84. The MON number is always lower but not by such a huge amount.

Note that as a comparison the MON number of 91' pump petrol is 82, not a lot different.
Would you run your motor on straight 91'?
The respective anti knock index ratings are also not that encouraging.
Note that although the spec sheet is written / itemized a little differently for No. 1 / Avgas, but in fact the RON number is typically within 105 - 110
even though they don't rate Avgas in this way. The MON number is 100 or more, which is exactly the "territory" you need for your motor.
Note that BP "Ultimate 98" is an "Environmental" fuel, it is not marketed as a racing fuel as such and has low benzene count.

So there you go
folks, always be very aware of the octane sensitivity of your racing 2 stroke. Some motors may run happily on pump fuels but many are very sensitive and can detonate quite readily due to a whole host of variables.
Many of the late model highly tuned 2 stroke MX based bikes require at least
a 50% concentration of Avgas and 50% 96. Those most sensitive to detonation will require an even higher concentration and so on. As Avgas has a slower burn speed it is popular to use "cocktailed" with pump fuel to raise the burn speed for decent
engine response.

The flip side is that with very high concentrations of Avgas, reed petal life becomes shortened."

The other factor to be aware of is that in the autumn months fuel companies change the volatility of their fuel for easier starting in cold weather. "The fire lights easier" and burns more rapidly. This is no problem for your average passenger car, which accounts for 99% of the fuel company's market.
However, this can very often can be detrimental to a highly tuned racing motor, engine problems can suddenly appear in the
autumn months that weren't there during the warmer months.

By law of averages we are just a small minority and a relatively small annoyance to fuel companies who are only concerned about a bigger picture.
Nothing is ever as simple as it seems......................


I find it interesting that when approached at a technical level, BP say they market 98 as an environmental fuel, but in actuality, looking at the adverts for it at their stations, they seem to market it as a "fuel for performance vehicles"

Oh well, time for time to go and have a good cry and work my ass off to get some $$$ to do it all over again.

Sugilite out!

[Snowcarver04]

I had a Cbr 250 R before i wrote it off bout a month ago but I was always told a high reving machine (19,000rpm) should always use the 98 fuel. I noticed more power and it is a lot better for your engine.So it really doesnt matter whast fuel you use in a low reving engine

[Morcs]

I started using 95 for a bit. ran ok.

Used 98 for a few tanks, was pining.

Went to 91, after running fuel set through the system (cleans all the shit etc.. out of your tank and carbs) and its been running really well. throttle is a lot more responsive. And thats on a 16k redline bike.

[lukelin250]

ive read all the comments and im still confused. someone do a dyno test as i think this would be the most conclusive evidence

[The_Dover]

are you fucking retarded?

in order to get more power from a fuel (assuming the engine is properly tuned) then it would require the fuel to have a higher calorific value.

put what teh fuckin manufacturer specifies in the heap of shit and ride it.

[lukelin250]

100 proof absinthe dover???

or your piss?

dyno test that ehh :rockon:

[The_Dover]

my piss by a cuntry mile.

and it's probably better to wino test it.