Running any fuel that has a higher octane rating than recommended by the factory will result in lower overall power output, higher cylinder temps, and a lighter wallet.
The best thing I can see about running a "race fuel" of proper octane rating is that one would always be assured of getting the same fuel every time, without the seasonal blend changes that are prevalent in many states.
I have written several posts about "Octane" and fuels on this forum in you want to sear them out. Or do a Wiki search for Octane, there is a great article there that explains the different measurements of Octane, MON or motor octane, RON or research octane. And the methodology of determining an Octane rating for a given fuel.
The basic rule of thumb is to run the fuel with the lowest octane rating you can get away with. It will deliver the most power for a given fuel charge, and generate the least heat in the cylinder. And when running at higher altitudes, you can run a lower Octane fuel as the cylinder pressures will be lower on a normally aspirated engine.
Please read the tech article associated with any of the VP motorcycle fuels.
http://www.vpracingfuels.com/motocross.html
The following is lifted from that Tech article:
You can't make a racing fuel that has the best of everything, but you can produce one that will give your particular engine the most power. This is why we produce different fuels for different applications. The key to getting the best racing gasoline is not necessarily buying the fuel with the highest octane, but getting one that is best suited for your engine.
1. OCTANE – This is simply the rating of a fuel’s ability to resist detonation and/or preignition. Octane is rated in Research Octane Numbers (RON), Motor Octane Numbers (MON), and Pump Octane Numbers (R+M/2). Pump Octane Numbers are what you see on the yellow decal at the gas stations and represents an average of RON and MON. VP reports MON ratings because this method tests a fuel’s performance under a heavier load than the RON method, thus better simulates racing conditions. Most other companies use RON because it sounds better in marketing messages. Don't be fooled by high RON numbers or an average—MON is the most relevant for a racing application. However, a fuel’s ability to resist preignition is more than just a function of octane.
2. BURNING SPEED - The speed at which fuel releases its energy. In a high-speed internal combustion engine, there is very little time (real time - not crank rotation) for the fuel to release its energy. Peak cylinder pressure should occur around 20° ATDC. If the fuel is still burning after this, it is not contributing to peak cylinder pressure, which is what the rear wheels see.
3. ENERGY VALUE - An expression of the potential in the fuel. The energy value is measured in BTUs per pound, not per gallon. The difference is important. The air:fuel ratio is in weight, not volume. Remember, this is the potential energy value of the fuel. This difference will show up at any compression ratio or engine speed.
4. COOLING EFFECT: The cooling effect on fuel is related to the heat of vaporization. The higher the heat of vaporization, the better its effect on cooling the intake mixture. This is of some benefit in a four-stroke engine, but can be a big gain in two-stroke engines.
It looks like the MR PRO-5 would be about the best choice for our bikes.
I run Chevron 91 gasoline and have had great success with this fuel over the 130 hours that I have on my 09 570. This fuel has noticeable improvements over the Shell 91 that I was running before.
