hedwards

It's worth noting that gasoline without preservatives has a relatively short shelf life when improperly stored.. And the high octane gas tends to sit around longer than the cheaper stuff does.

I'm not sure how much faith you can put in proper storage in a tank designed to be routinely drawn from. Consequently using the higher octane stuff can have an impact on the performance of the vehicle.

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GearJammer

Absolutely agree with you, jax......When I first got the 450, was running 91 octane, then while topping off at the gas station one day, some guy on an XS650 was putting 87 octane in his bike and mentioned that it didn't require the 91.......Started using 87 after that for awhile, but a couple rides ago, had been running the 87 for one stretch of the ride and then decided to top off with 91 octane for the return run. The bike ran MUCH better, so it's back to 91 octane again (at least on the 450)

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"Ridin' Ain't A Hobby, It's A Lifestyle"

1986 450 Rebel

Rebelgirl1978

I just use the regular 87 octane in both my bikes

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1985 Honda Rebel 250
2008 Honda Rebel 250

twocoolgliders

The bull-sh-t-o-meter is readin in the "high" zone! Urban myth!

Can anyone provide some substantial evidence as to the scientific or engineering basis for higher octane giving any performance increase of any kind, when used in a "regular" octane engine?

Octane is simply an anti knock rating........if the engine doesn't knock with regular, that the end of the story..........won't knock with high octane either, but there is no more power or economy or "better running" in higher octane either.

BTW....I just love the scientific term, "runs better"......what exactly does that mean?

OK......waiting for the arguements.....lol

Cookie

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maxweljames

twocool, anti knocking is actually a byproduct of higher octane ratings. As the octane level goes up so does the auto ignition temperature. Auto ignition is bad in a spark ignition system style engine. We only want the spark plugs causing the fire, not the heat from the cylinder walls.

What does all this mean for getting more power. The higher the octane the slower the ignition. A lower octane has a much faster burn rate and uses up it's energy before the piston produces it's full potential. You are correct that even with 87 there is no knocking, meaning there is no pre-ignition of the fuel. But by stepping up the octane, slowing down the burn we create energy over a larger time frame, allowing more power to be developed.

Mind you all this is happening faster than you can blink. An internal combustion engine is a beautiful thing, and we're fine tuning how it operates simply by changing the hydrocarbon level we induce into it.

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Maxwel James
2003 Honda Rebel

Blueberry

I use high octane in my Royal Enfield. Its a 500 single with a 90 mm stroke. It burns slower pushing the piston for a longer time. Slower burning also cools the piston and cylinder walls longer. I can kick start it in 1 kick hot or cold with high octane. Not so with regular. It helps in an engine that fires every 720 degrees of crank spin. The Rebel and 90 get regular. It burns faster and on a short stroke engine high octane can still be burning past bottom dead center and result in a drop in power and mpg. When all is said and done, run what you feel is best for your motorcycle.

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Ride Safe, Blueberry
1985 Honda 250 Rebel
1970 Honda SL 90
2008 Royal Enfield Electra 500

cagie

This is true for a longer stroke engine where the higher octane actually has time to burn. The Rebel is a short stroke engine, so higher octane is a was of money as the slower burn doesn't do anything for the engine.

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Comments contained in my posts are not intended to cause physical or psychological stress and are mearly my two cents worth, and in this economy, that's cheap!
87 CMX250C 'the Pygmy Pony'
87 CMX450C 'Black Lithium'

maxweljames

A very good point cagie. It's such a micro level we're talking about. And outside of the actual fuel we have air temperature, pressure, humidity, etc. to concider. Blueberry makes a good point too, higher octane generally burns cooler, this adds to the efficiency of the engine as well.

All in all there will be days when the Rebel just seems to run a bit better, enjoy those days my friends.

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Maxwel James
2003 Honda Rebel

GearJammer

Did I mention anything about "anti-knock" ? The 450 didn't knock on 87 octane and doesn't knock on 91 octane, but it DOES "run better" on 91 octane. Don't care how you slice it, I know my own bike and how it performs...........and whether you like it or not, or believe it or not, it RUNS BETTER on 91 octane......

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"Ridin' Ain't A Hobby, It's A Lifestyle"

1986 450 Rebel

hedwards

If it doesn't knock at 87, it shouldn't knock at 91.

I'm curious on what way does it run better?

AFAIK the main issue is that of timing and compression. I don't personally know of any reason why the suggestion of the manufacturer wouldn't be correct, unless there's been some adjustments made in terms of aftermarket customization to change that.

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