Can I change fuel to different octane?

**seoky** · 13th October 2013, 17:31

Hi.

Is it bad for the engine if I run my gt250r on 95 octane from 98?

From research it depends on the compression ratio of the engine which I have no understanding of. haha
And running 98 right now may possibly be not good for power.

I have to gradually change to 95 right? (increase 95 to 98 concentration)

Thanks champs

**russd7** · 13th October 2013, 17:37

wont hurt your bike and no you wont need to do it gradually, you should be able to run 92 octane in it as well, its not a high performance bike
we dont get 98 down here only 92 and 96

**Danzano** · 13th October 2013, 17:43

Stock compression for that bike would be 91 octane but if it can auto advance or retard the ignition then 95 is ok to 98 will work but no benefit I would say 91 unless your looking at mods but it will probably make the most off 91 as like most bikes it's tuned for the states 89octane

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**The Reibz** · 13th October 2013, 17:50

Put 2 stroke mix in it. Fuck it will go hard, will root the motor but ah its a Hyobag. Not even a real bike anyway

**AllanB** · 13th October 2013, 17:57

Recon you are wasting your $ on 98 ..........

**ozjohnno** · 14th October 2013, 10:50

A good question and the answer is NO, you cant wreck your engine moving from 98 down to 95. It might be a different story moving down to 91. This will cause your engine to knock under load and lets face it, its a 250 so you're gunna have to wring its neck to make it go anywhere quickly. In an emergency however, 91 is better than walking, you just have to be more easy with the throttle.

**ozjohnno** · 14th October 2013, 10:52

A good question and the answer is NO, you cant wreck your engine moving from 98 down to 95. It might be a different story moving down to 91. if the octane is too low it will cause your engine to knock under load and lets face it, its a 250 so you're gunna have to wring its neck to make it go anywhere quickly. In an emergency however, 91 is better than walking, you just have to be more easy with the throttle.

**Ender EnZed** · 14th October 2013, 11:13

You could drain the tank completely and fill it with 91 and you'd be unlikely to notice any difference. 95 will be absolutely fine.

Don't worry about it unless you've just filled the tank from near empty with diesel.

**iranana** · 14th October 2013, 11:34

The higher the octane, the more compression it can withstand before ignition. Low octane fuel in a high compression engine will pre-ignite, causing engine knock. You can hear engine knock pretty clearly. As far as I understand (which isn't a hell of a lot) the only point of running high octane fuel is so that you don't blow up your high compression engine. I think high octane fuel also burns cooler than low octane, so for high stress running it keeps the engine a little cooler. I don't really see why you're running it on 98 to begin with, since the stock compression ratio probably isn't very high. I'd hazard a guess that the fuel isn't burning as efficiently as it could be you'll be getting crappy mileage from expensive fuel.

**ozjohnno** · 14th October 2013, 16:20

wherever possible I run my multistrada on 98, although I have used 91 in an emergency. All you gots ta do is take it easy on the throttle. it you hear it start to knock, back orf lil bit.

**Transalper** · 14th October 2013, 16:40

If this manual (link below) is correct for your bike it says to use anything 91 or higher so yes... that would include 91 being fine.
www.hyosung.com.au/downloads/manuals/GT250.pdf
The EFI version may be different, you didn't say what year it is (or have i missed that).

**ellipsis** · 14th October 2013, 17:04

...oh cool...an opportunity to recount a story about fuel and octane levels...mid 70's when my trade was in a big down I worked for a while at Shell Oil in the area of bulk distribution...oil tankers, trucks and 44 gallon drums...an older, near retired truckdriver who did pickups of the 44 gall drums that were Shell's, had a Morri' thou...we saved, just for him, a 4 gallon tin of dregs we sucked from the avgas empties that he brought back from the airport...we also put a bit of other shit that we took from drums before they were put through the wash...like toluol, isopropyl alcohol and whatever other chem shit we had to fill his 4 gall tin...every friday arvo he would put it in his morri...it ran like a dream, the pipe was running a grey/white colour and he had been doing it for years....

**ducatilover** · 14th October 2013, 19:42

Originally Posted by ozjohnno

A good question and the answer is NO, you cant wreck your engine moving from 98 down to 95. It might be a different story moving down to 91. if the octane is too low it will cause your engine to knock under load and lets face it, its a 250 so you're gunna have to wring its neck to make it go anywhere quickly. In an emergency however, 91 is better than walking, you just have to be more easy with the throttle.

91 won't hurt it, this isn't 1974.

**Theantidote** · 14th October 2013, 19:53

contrary to all expert advice i have been running the viagra on 91 since i got her...no knocking or loss of power...despite what people keep telling me...i did read of lead memory in engine blocks and other such wifery type tales but for me she runs, runs as well as she can and i love riding her (the viagra not my wife...oh hang on that came out wrong)