Will running a higher octane fuel in my pred (and trailblazer for that matter) increase performance? Ive been told that running a higher octance is useless and could actually decrease performance unless you increase compression....but I dont know for sure...jsut wondering what some of you guys think.

 

A lot of people say it is useless but i also heard for 2 strokes it is better to run higher octane fuel.

 

Its a waste of money unless the engine (or the parts in the engine) is designed for the higher octane. Doesnt the Pred require Premium anyway?

 

In the manual it says to run no lower than 87 and no higher than 93...so i wasnt sure what was better

 

Just run the midgrade them. With the price of gas how it is, run with what you can get away with

 

it all depends on how much compresion you have ... i dont no much about predertors but in 400's when your runnin a bigger dome its nice to be runnin higher octane .... if your runnin a 12:1 dome i would probably put it on aviation fuel ... and 14 and 15:1 domes i would sugest runnin race fuel ( 110 ) and if your runnin the 15 or 14 and on regular premium fuel its not gonna run right .. austin

 

Simster570 you are right. You can mix 110 and 92 half and half and it will run a little better but not enough to go to all that trouble...just use the 92 in the pred and the trailblazer.

 

Taken too extremes, too much octane will actully cost you power.
You need good enough gas to prevent detonation, preignition and so forth.
One real advantage of "good gas" is consistancy.
Cheap pump gas can really vary and cause tuning problems.
This is where race gas or avgas will make your life a little easier of you are working with your jetting.
However stock machines usually will run just fine on premium unleaded.

 

The stock compression ratio of the pred is 10.8:1 thats pretty close to 11:1 anything over 11:1 its a good idea to run race gas. But in the case of a stock predator midgrade is fine...

 

In the case of my RoadStar Warrior, 87 octain is what is recomended. A friend of mine put his RS warrior on the dyno and did runs with both and believe it or not, he had a performance drop when using 97octain. In the case of my Sled, which is a two stroke and my Scram 400, I can literally tell the difference between a higher octain and lower octain, higher octain gave a better performance. Octane rating is a resistance to ingnition rating more or less. In a high compression engine the compression of the fuel air mix raises its temp, then when ignition takes place a flame front expands from the spark plug, (ever see fuel vapors on the ground ignite and a blue ring of flame spread out?). As the flame front expands and consumes the fuel, the heat increase raises the pressure of the gas, this increases the temp of the yet to be burned fuel, which was aready hot from compression. If the remaining unburnt charge reaches a critical temperature and pressure, It will spontaneously explode, all of it igniting at once and producing ping or knocking sounds. There is also a factor of time involved, so that this happens more easily at low rpm's. A high octane fuel has more reistance to ignition than a low octane fuel, thus imparting more resistance to knock, however there is a down side in that the higher resistance to ignition tends to give a slower flame front travel speed, possibly slowing complete combustion. This can result in a small, but measurable loss of power. Generaly, engines poduce their best power with fuel octane rating that is adequate to prevent knock but not much more. Running high octane fuel in an engine that doesn't need it can result in a slight loss of power and at best is just a waste. (Assuming all other additives are equal.) In short, no ping on regular equals no need for premium.