Octane - what is best?


14 replies to this topic
  • RD73

Posted January 18, 2006 - 10:25 AM

#1

Octane is added to gasoline and it slows the burn or detonation. Higher octane prevents preignition, so higher ratings are needed for higher compression engines. Higher ratings, the slower the burn when ignited during the compression burn cycle of the piston.

In short, more octane does not equal more power.

It seems that a lower octane rating, since it burns faster, would make more power. However, you should run a high enough octane to prevent the bike from pinging.

What do you guys run and think?

  • 450GN

Posted January 18, 2006 - 10:33 AM

#2

i run premium 93 octane... available everywhere
race gas benefits the high compression and boosted applications as you stated... which i run in my car frequently
but as for low octane... it doubt it would make a difference in HP since i dont think even 93 has that much resistance to burn to make a difference..

  • bruntz505

Posted January 18, 2006 - 11:02 AM

#3

I use unleaded plus(ethanol) @91.That is the highest rated gas we have here.I tried 110+ race fuel in my 450 and 250,and they both ran worse!What is that 93+ rated fuel that you can buy at Amoco stations?I'd like to find some of that.

  • beezer

Posted January 18, 2006 - 11:18 AM

#4

A buddy has a RPM CRF 302 and they said to run 93 octane in it but on SX style tracks the 91 was a better choice. It would pull harder out of corners with the 91.

  • 642MX

Posted January 18, 2006 - 11:21 AM

#5

I run 110 octane leaded, but my compression ratio is 13.5:1. I've been using it for years with no problems.

  • brycee

Posted January 18, 2006 - 11:58 AM

#6

These bike are designed to run off Pump gas.... until you're running higher compression you don't really need to run higher octanes. Although, race fuels designed for 4-strokes, such as VP ultima-4 have been said to gain as much as 4 horse simply from running the fuel. It's not much higher in octane... but I understand that it's oxygenated which helps the burn especially.... right?

  • roostmonster

Posted January 18, 2006 - 12:11 PM

#7

In my 99 YZF 400 I found that it ran better and started easier using VP MS-103. I think it is rated at like 99 pump octane. In my 04 CRF 450R I run nothing but premium pump gas. Here you can find 93 octane all day long. Bike runs great. :thumbsup:

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  • Diode663

Posted January 18, 2006 - 12:43 PM

#8

You also have to jet correctly for your fuel. Otherwise you wont be seeing the benefits of higher octane and oxygenation (unless you dont need it).

  • grayracer513

Posted January 18, 2006 - 03:15 PM

#9

The flaw in your logic is that octane has nothing whatsoever to do with the burn rate, flame temperature, ignitability, or energy content of the fuel, or anything else at all except the fuel's ability to resist ignition from sources other than an open flame or a spark. High octane fuels that are bought outside of the normal gas station outlets may be different or perform better in any or all of the above ways, but because of their higher overall fuel quality, not their octane number. VP U4, for example, is usually worth 1-2 HP in a properly jetted 450 compared to pump, but it's only a 92 octane fuel.

If the octane is high enough to prevent detonation and pinging, it's high enough, and spending money to get any more is a simple waste.

Read This to learn more.

  • yz250ftony

Posted January 18, 2006 - 03:30 PM

#10

I run 110 leaded, stock C/R, but everything done to the motor. Jetted with a powershot. I run the higher octane because I ride at upper elevation. Runs better with it, doesnt like pump gas.

  • Jetsprint2

Posted January 19, 2006 - 08:08 AM

#11

I run 110 octane leaded, but my compression ratio is 13.5:1. I've been using it for years with no problems.


Guys like this that have bumped up the compression are the only ones that benefit from high octane race gas. I have a stock 04' 450 and run premium 91 octane and have had no problems as everyone else I know of in my area. Here in Boise 91 is the highest rated octane available straight out of the pump. Make sure you get your gas from a high volume pump so you can at least get fairly fresh fuel. There is 94 around but it is a different formula and it has methol in it, don't really know much about that so I steer clear of it. :thumbsup:

  • RD73

Posted January 19, 2006 - 09:29 AM

#12

[quote name='grayracer513']The flaw in your logic is that octane has nothing whatsoever to do with the burn rate, flame temperature, ignitability, or energy content of the fuel, or anything else at all except the fuel's ability to resist ignition from sources other than an open flame or a spark. High octane fuels that are bought outside of the normal gas station outlets may be different or perform better in any or all of the above ways, but because of their higher overall fuel quality, not their octane number. VP U4, for example, is usually worth 1-2 HP in a properly jetted 450 compared to pump, but it's only a 92 octane fuel.

If the octane is high enough to prevent detonation and pinging, it's high enough, and spending money to get any more is a simple waste.
QUOTE]

Thanks for the link Gray. I did some reading about octane on-line (well it was posted on the Internet, so it must be true :thumbsup: ) and posted my question. Without disparaging the author, I can say that he or she was partially correct about Octane, but wrong about it impacting the burn rate.

Sometimes it is better to start with a statement (my original post) from which others can disagree to arrive at right answer. The link you provided cleared up my understanding of the subject. There is even a section on the "moth ball" rumors I have heard for years!

Regarding your response, I was wondering about pump gas, as I ride a street bike as well as a dirt bike. Thus, I was trying to determine what is best choice at the pump, since it is unlikely I will be filling the street bike with other fuels (even if those fuels are superior).

  • Justa4stroken

Posted January 19, 2006 - 10:06 AM

#13

I run Turbo Blue :thumbsup: , 110 octane racing fuel. Has a research octane rating of 115 octane, in my wr450 with Hotcams,FMF silencer, Jetted.

  • grayracer513

Posted January 19, 2006 - 12:56 PM

#14

RD,

I like Hamilton's article. As technically deep as it is, it's still readable by most people. There are 4 parts to the entire thing that you can get to if you backtrack the URL a step that together tell the whole story.

I'm not sure how different practices would be in SC, but here in Southern SoCal, this is how it works:

All of the gasoline sold in the greater San Diego area arrives at a tank farm in Mission Valley in one of two pipelines, one for premium, one for regular (mid-grades are mixed as they pump at the retail station), and is stored in the tanks there for distribution. All of it. It comes from all of the various refiners, Shell, Chervon, Exxon, etc., but it ends up in the same place, and it's all absolutely the same.

Tanker trucks get an additive package dumped in the empty tanks as they leave their yards to fill up, and each different brand fills their trucks from the same tanks. Every one of them. Then it's off to the gas stations to deliver the goods.

So, the fact is that Chevron, ARCO, Costco, Thrifty and Wal-Mart is all the same stuff except for the additive package, which, I admit, can vary some what, but among the Majors, it's pretty much the same from brand to brand.

So given all that, chose a pump gas in your area that works the best in your bike, and doesn't cost too much more than the next brand, and is reasonably consistent. ( I usually run ARCO, I run Chevron now and again, and I'm not above using what I can get in a pinch). Even the guys I know who have gone to 13.5:1 run pump stuff with no trouble. The point about buying from a volume seller is valid for the reason stated; it's probably going to be fresher.

  • ONLY4STROKES

Posted January 19, 2006 - 01:12 PM

#15

I run 110 leaded, stock C/R, but everything done to the motor. Jetted with a powershot. I run the higher octane because I ride at upper elevation. Runs better with it, doesnt like pump gas.


That's odd...the higher the elevation means less octane is needed.

Please explain?





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