Professor

I stopped at a Texaco in Gastonia, NC (near SC border), and they had 100 octane gas for $6.99 per gallon. I was dead empty and started to put 3 gallons of 100 and 3 gallon of 93 in the RL, but I was chicken.

I was afraid the 100 proof stuff would eat up the stock fuel lines, burn a piston, bend a valve stem, etc.

So if anyone goes through Gastonia in their RL, get some of this gas and tell me how it does.

bugeye

I'm not positive, but I don't think 100 octane would hurt your engine, per se, but I also don't think it would do anything good for you either in terms of power.

Now, when I used to put 100 octane in my tricked out Subaru.... 22psi and the car would pull like a beast.

Ken1997TL

Exactly, 100 octane will only improve the performance of a high strung motor thats been tuned for such things

Juiced46

Exactly what these guys said. 100 octane will actually make your car slower if not tuned properly. If you just pump in 100 octane without adjusting the Air/fuel ratio, or timing you will actually lose power. The higher octane fuel will make the car run more rich, and cause a loss in gas mileage. It will not hurt anything, like your fuel lines etc etc

acuda

Higher octane formulations are actually less combustible than lower octanes. As has already been implied, the only benefit comes when used in engines with high compression ratios where lower octane blends would pre-ignite (knock) from the compression alone.

Ballinger

Holy Smokes! The higher octane-rated gasoline you're talking about is neither "less combustible" nor able to alter your fuel-air ratios. You can run it without any problem other that wasting a little money.

"Octane rating" is effectively a way to tell you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it's called knocking. The RL, like many cars, will sense this and retard the timing to prevent it because predetonation can damage an engine. This lowers performance and gas mileage. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.

Higher octane gas sometimes gets there by the addition of MTBE, which also cuts into your mileage, since it reduces the explosive power of the gasoline. Better "high test" fuels use additives like xylene to boost the resistance to spontaneous ignition and allow the properly tuned motor to utilize higher compression and then bang the gas with a spark when it's ready to. Octane rating doesn't make the gas more powerful, but allows your motor to detonate it with a spark when it's ready. Higher octane-rated gas than your motor is tuned for is just burned with the spark plug ignition, the same old way at the same old temperatures --without any extra power resulting.

If one were to run AvGas or other Very High Octane gasoline, there is an alteration to the fuel-air mixture, but this is less than insignificant in fuels under 105 Octane, especially where the "booster" isn't ethanol.

Best bet for the RL is to run the 92 or so "premium fuel" and just pay the 2-3 bucks a gallon.

acuda

Thanks for that correction and explanation. More "detonation resistant" or "requires a higher activation energy" would have been better choices than less combustible.
Higher octane ratings correlate to higher activation energies. Activation energy is the amount of energy necessary to start a chemical reaction. Since higher octane fuels have higher activation energies, it is less likely that a given compression will cause detonation.

Chas2

Thanks to you both for the concise and understandable explanation.

Professor

I'm glad I bought a Snickers and Coke instead.