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91.

now its mandatory 91 +10% ethanol i use 95.

i don't like it.

theres no benefit to using anything higher than 91. unless you are getting pre ignition. but then you have other issues.
 

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I use Caltex Vortex 95. You're probably better off using 91 or 95 octane because the engine is old, but if it runs fine on 98 octane and you've got the money to spare then it's probably better for it.
I've been wanting to try 98 octane in my MC19 and I'll probably do it the next time I fill up, but mine runs pretty much the same on both 91 and 95 octane.
 

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Mr5un said:
does 91 contain ethanol?!?!?!?!
shit
i didn't realise that.
for example shell in melb has it's own e10 for ethanol and 91, etc.
didn't realise 91 contains ethanol
you're not confused.
it may seem that some Shell stations are still providing unleaded 91 octane (no ethenol) as well as e10. The Shell station near my work has both, with it's e10 being 94oct + 10% ethanol. I actually thought that it was my petrol station that was the only one that was providing normal 91 octane unleaded as no other Shell station seems to be doing it here in Sydney.
 

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i don't have an issue with ethanol per se, its just that i hear anecdotal evidence that the acidic nature of ethanol can swell rubber. if you have a thin rubber diaphragm in your carby (as you do, if you have a cbr) then replacing fucked rubbers comes in at around 80-100 a pop.

SMOKEU said:
I thought that a high performance engine like these might detonate on 91, that's the only reason I use 98.
lol, ours really aren't that high performance. consider that they were built when 91 RON was the norm. i use 95 now because i can't find ethanol free 91

aus36 said:
Mr5un said:
does 91 contain ethanol?!?!?!?!
shit
i didn't realise that.
for example shell in melb has it's own e10 for ethanol and 91, etc.
didn't realise 91 contains ethanol
you're not confused.
it may seem that some Shell stations are still providing unleaded 91 octane (no ethenol) as well as e10. The Shell station near my work has both, with it's e10 being 94oct + 10% ethanol. I actually thought that it was my petrol station that was the only one that was providing normal 91 octane unleaded as no other Shell station seems to be doing it here in Sydney.
you may notice that some petrol stations are shutting down for refurbishments? that because there is a government mandate that all 91 must contain 10% ethanol. not sure if that is NSW or federal.

SMOKEU said:
We don't get ethanol in our fuel over here.
half your luck. like i said, i don't have a particular problem with ethanol, as long as it doesn't affect food crops. but thats another issue altogether.
 

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It might be high peformance with respect to power for its size, and its rpm range, but its still an old engine, these engines were made for 91 Octane, infact afaik, 95 and 98 RON weren't even available when the 2fiddy engine came out in the 80's.

98 RON should only be used in engines that have a high compression. see here:

"Octane rating does not relate to the energy content of the fuel (see heating value). It is only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. Where octane is raised by blending in ethanol, energy content per volume is reduced."

"Higher octane ratings correlate to higher activation energies. Activation energy is the amount of energy necessary to start a chemical reaction. Since higher octane fuels have higher activation energies, it is less likely that a given compression will cause autoignition.

"It might seem odd that fuels with higher octane ratings are used in more powerful engines, since such fuels ignite less easily. However, an uncontrolled ignition is not desired in a spark ignition engine."

"Many high-performance engines are designed to operate with a high maximum compression, and thus demand high-octane premium gasoline. A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power."


Basically, whatever the CBR Manual says to use, will give you the best performance, for those who say their bike runs shitty on 91 or 95, its probably because 98 is harder to burn, and likes to stay behind in a lower compression engine, can apparently clog shit up Ive heard.
 

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BriZer said:
Ninexz said:
my mc19 shits its pants on 95 so I have to use 98. Runs nice on that.
BP ultimate
+1 .. Tried it when i was low on cash and I will never be doing that again.

Ethanol + old engine = Runs like a bag of shit

BP Ultimate unless im desperate
I accidentally put e10 91 octane in my MC19, once and it's never run better than it did on that tank. No idea why though. I guess our bikes all like different fuels lol
 

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I run my mc19 on 98. As for people complaining about the money, you must be a real tight arse as it only uses a fraction of fuel that a car uses. And i thought that Japan only had 100 octane or something like that? (might not be true) Anyway i have always used 98 and i probably always will. Just ask a mechanic what they would use and if your bike got tuned with a certain fuel then wouldn't that be the best fuel to use?
 
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