?Which octane gas to use?

[jaguar]

I think my bike is more powerful with octane near 90 vrs using gas with octane near 95.
What's your experience?

 

[Jim Crenca]

I've had the best results with VP C-12.
My 94 also likes Sunnoco 94 octane.
Jetting for the brand of fuel will make a difference in performance.
BTW, when you say more powerful, I'm assuming you mean better throttle response. I don't find any total HP increase with any pump or aftermarket fuel.

 

[twocycle]

It is my understanding that the lower octane fuel burns more quickly.
The higher octane fuels burn slower therefore resist detonation better in
higher compression engines.

 

[jaguar]

Yeah but unless you've increased the compression it could be that the high octane fuel burns too slow for us KDXers.
C'mon, let's here others opinions (if you have experimented with both types pump fuel).

 

[Boot]

Actually, the octane rating should really have nothing to do with the rate of burn. It's purely an anti-knock index - the ability of the fuel to resist self-detonation. In these lead-free days, it's often achieved by using more aromatic (ring structure) hydrocarbons like toluene and fewer straight-chain varieties. Once you find an octane rating that prevents your bike from pinging, anything higher is a waste of money. A lot of people use higher octane fuel thinking that they're doing their vehicles a favour, but it's just not the case.

Of course, it could be that in some places the higher octane fuel also happens to coincide with some other factor that makes the fuel better quality or burn at a different rate. But you can't then make blanket statement about all brands in all places based on the octane number.

 

[Jim Crenca]

Search in Advanced Tech for many threads on fuel chemistry and dirt bikes.
Also, Rich has a great Fuel Article on Eric Gorr's site.
Trust me, if you do the homework there will be no more fuel questions :aj:

 

[skipro3]

Jim is correct. Rich has some great stuff here on fuel and C-12 in particular. I've discovered that the consistancy in the fuel from tank to tank keeps my jetting straight on. I now have almost zero spooge, and the bike barely smokes even when first started. No way I could jet this tight on pump gas and the variances from fillup to fillup. Throttle response reflects the accuracy in jetting but I do not detect an increase in felt HP. I can now take a 4 hour ride and afterwards, check the exhaust outlet with a towel and have a little soot but no spooge. Verrrrry clean.

 

[jaguar]

I just saw at www.ericgorr.com this fuel recommendation for the type of poerband the bike produces:

Low To Midrange: Super unleaded 93 octane

Midrange and High-Rpm: Racing fuel 105 octane

 

[JCW]

Personally, I like higher octane fuel. In my KXs and KDX higher octane fuel seems to give better throttle response and it doesn't seem to load up the plug if you are going slow in a technical area. Although KDXs don't really foul plugs, KXs really foul plugs on lower octane fuel (even with correct jetting). I'd love to run race fuel all of the time, but I'm too cheap to pay the price and it's a hassle to go get.