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Jim_bo

95 Octatne Gas???

14 posts in this topic

The WR450's owner's manual calls for 95 octane gas. Where the hell do you get that from? Most pump premium is 91 with some places sellng 93. But I have never seen 95! Do I need to buy race gas for a stock bike??

Jimbo

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I run 1 part 91 to 1 part 100 for 95.5. Some of the 76 locations in my area sell the 100 octane competition fuel. I hear alot of people just run premium (91,92,93,94 depending on elevation) but to me 12.5:1 compression is pushing it for just premium alone. These bikes don't have a dynamic ignition system that will retard timing if detonation occurs and loud exhaust pipes could easily drown out the sound. Or maybe its just because the comp fuel is blue too :).

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One thing to keep in mind is that there are different methods to determine the Octance rating. Research octane is rated differently than pump gas. That is where the discrepancy could play in I believe.

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There are three rating for octane that I know of Research, Method, and the one on all the gas station pumps I have used R+M/2 (which is just an average of the first two). I can only assume that since these bike are delivered to the USA that the specs in our manuals should be for the ratings we use. 12.5:1 is high compression for a gasoline engine, most cars that require premium are around 10.5:1 with advanced engine management systems. In my opinion pump premium is on the edge at best.

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Move to Europe and get good gas!95 Octane in MINIMUM you can buy at the pump.The other choice is 98!

However I'd take your gas any day as here in Switzerland it costs approx 1$/litre (Approx 4$/gallon) at current exchange rates - and we have the cheapest gas in Europe!

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92 pump gas is fine but if you want a cleaner burning fuel, check out www.vpracingfuels.com It will cost more ($6/gal +/-) but there are numerous posts stating that engine performance is much more consistent and jetting is therefore easier.

Some people do a 50/50 mix just to keep the costs down. I plan on trying that for awhile this summer. :)

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I run exclusively Conoco's premium 93 octane pump gas. Without pulling out the text and reviewing octane measurement methods, I believe the method used in U.S. gives a slightly lower value on the same gas, than the Research method referenced in the Yamaha manual. Thus 93 pump gas is about 94 Research method. Close enough, and it runs fine. You may have to adjust to slightly richer jetting.

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Just a follow-up question: I pulled the manual out and it states to run unleaded fuels only and that leaded fuels will damage the engine. That seems a little contrary to my thoughts, as I thought lead was a lubricant and therefore it would be beneficial. Anyone have any idea of the type of damage a leaded fuel could cause and why? All the VP fuels carried by my local dealer are leaded.

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It plugs up the catalitic converters on the California models :) I am guessing it has to due with deposits and tight clearances.

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Jim bo,

Pumps in the US (and maybe Canada?) use the (R+M)/2 method for octane ratings - also called the antiknock index or AKI. R=research octane; M=Motor octane. The rule of thumb that everyone uses (recommended by the major petrochemical companies like Chevron) is to add 5 to the AKI to get the Research Octane Number or RON.

So, in the US, 91 AKI at the pump equates to 95 RON which is what the manual specifies as the minimum.

Hope that helps.

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Okay Okay... Evidently I have forgotten how to add.

I meant AKI of 91 gives 96 RON which is actually one point higher than the minimum in the manual. I guess that's what I get for posting this late at night. I even reviewed the post before I sent it. Geez!

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