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High octane gas necessary for dual-sport?

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I recently rebuilt my 1979 XL250S with all OEM parts and it is almost a completely stock bike. I have always been told to run high octane fuel in motorcycles, however I'm curious if that is true. It is an air cooled kickstart bike, would I be better off with high octane or does it really not matter?

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Others may have a different opinion, personally I think your wasting your money on anything more than 93 octane on stock equipment. Use the extra money you save at the pump for oil changes.

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Others may have a different opinion, personally I think your wasting your money on anything more than 93 octane on stock equipment. Use the extra money you save at the pump for oil changes.

i believe he is referring to 93 as high octane fuel, i have always done it because my manual has required it

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over here the highest we get is 91, which is like 30 cents more then 87, so for 60 cents more, why not?

thats how i feel about it.

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I recently rebuilt my 1979 XL250S with all OEM parts and it is almost a completely stock bike. I have always been told to run high octane fuel in motorcycles, however I'm curious if that is true. It is an air cooled kickstart bike, would I be better off with high octane or does it really not matter?

if you run a lower octane fuel than your supposed to it can cause preignition or detonation because the octane in gas actually slows the rate at which the gas burns and lowers the flash point this way it can compress the gas/air mixture more before it ignites it self because compression creates heat, so yes for a high compression motor (most any motorcycle or dirtbike engine) you should run at least 91-93, if you run 87 it will in the least run alot hotter which can burn up valves and hole a piston and worst case scenario the detonation (which is an actual explosion before tdc rather than a smooth burn right as it reaches tdc and after) will cause your rod to bend or piston to shatter, sending chunks of broken piston into your bottom end and transmission.

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Yes, sorry for the confusion, I was referring to 93 as high octane. I don't know what I am "supposed" to be running but I always ran 93 in all my bikes and was just curious if it was worth it or not, getting close to 70MPG I will dish out the extra 40 cents per tank and get the premium haha

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Depends on the motorcycle....CRF230 recommended min. octane is 87, Crf250X recommended min octane is 91. Running lower octane in a motor that requires more can/will hurt the motor, Running higher octane in a motor designed to run on lower octane will not cause any harm, but has zero benefits. It will not get better mileage or more power from octane.

Edited by Jakeblues

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Best fuel is the lowest octane that doesn't det. Higher octane does not equal higher performance.

I usually throw 91 pump gas in my moto and sled just to be on the safe side. But I've run 87 in my bike without an issue before too.

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The service manual for a 1979 XL250S specifies fuel type = Petrol.

Geez people, it's a 1979 air cooled XL (as in non-high compression). It will run just fine on any fresh pump gas.

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