Someone asked why you would use 93 octane over 91, in Jersey I can't get 91 octane. I have choice of 87, 89, or 93 and some Sunoco's sell Ultra 94.

Leaving gas in the tank for a long period of time isn't good. It does break down over time, but it usually takes a long time, 6 months or more. If you don't think you'll run the tank empty by then just add some Sta-bil, it is a fuel additive to keep gas from breaking down. It is available at any automotive store and most hardware stores (for lawnmowers over winter)

 

Based on all the previous posts which were very informal. I'm going to go with the recommended 91 grade. Just for the fact that my beater (neon) runs 87. We don't have 89 up here so it goes straight to 91 and 93. And to think of putting the same gas in my neon as my s2k makes me a little nervous.

On an extremely hot summer day i'll probaby go with the higher octane. But seeing how the gas prices are continuing to rise...... i'll probably stay @ 91.

 

I'm gonna add my 2 cents about a month late....

I heard that you DO want to keep gas in your tank, even if its sits for a long time. Your tank will water and be worse off than if you were to have to gas breakup.

And as for the octane thing, if you buy a sports car, treat it like a sports car. If you're that concerned about gas prices, buy a hybrid.

 

How much difference would it make to go from 93 octane to 91. I was buying 94 all the time at sunoco (only place to sell that high grade in the del-val), but companies are slowly phasing it out. the sunoco I go to no longer carries 94, but the did bring back 91. so now its 87, 89, 91, and 93, but at $3+ bucks a gallon, thats a little insane considering I go thru about 2 tanks a week.

 

No difference from 93 to 91, because the timing is optimized for 91 octane. The premium in California and Nevada and ..., is 91 octane

 

so does that mean best power output outta 91

 

re the comment about using higher octane gas in the mountains.

Gas stations up above 5000 feet probably don't have any 91 octane gas and the regular gas isn't 87, it's 85 octane. Since there is less oxygen, the octane can be reduced a couple of points without an increased risk of knocking.

 

All I've got to say is if you want to run 87, you better be running a fram oil filter and some cheapa$$ mineral oil and changing it every 10k miles or when the engine goes dry, whichever is first. The octane of the fuel you put in your car is just as basic as those things and on the same principle. There are very few street cars that 'need' 91 octane more than the s2k. Don't go cheap on the wrong things and you sure as hell better not have some titanium exhuast on your car if you are runnin 8X octane.

 

Screw it I'm using deisel....it's all the same right?

 

Using a higher octane prevents preignition. Preignition is when the fuel in the
cylinder combusts on its own (before the spark plug ignites it). So your piston
is moving up and the fuel ignites and creates pressure against it before it
reaches the top. This is extremely bad for the engine. Timing will not save
you here because the spark plug wasn't the one that caused the ignition, it
was extreme heat and pressure. Higher octane fuel is harder to burn than
a lower octane fuel and that's why it's needed in a high compression motor.
You want the spark plug doing the lighting. Timing can only do soo much..

I only read page one and part of three so I hope this isn't a repeat..
Thanks
Mac