Hey, I want to run 93 octane in my car. I know that it is suppose to help with performance, but how much will this affect my mpg compared to 87? Also what's the long term effect it would have?

Yes i have an SS S/C

 

I am not sure about MPG, but when I switched from 91 to 93 I noticed that it smoothed out the idle. It was also more eager to rev. My mileage has been around 32 mostly highway. From 87, you are sure to see some performance gains, and lessen your chances of knock.

 

good to know, I just do a lot of city driving and would like my mpg to stay the same or be a tad bit better for the extra $$$

 

Definitely switch at LEAST to 89, 93 would be best though. GM recommends a minimum of 91 octane for the SS/SC, which they don't sell around here, so I have never put anything less than 93 in mine.

 

in my ss Manual it recomends 87 octane the higher the octane just mean s the more resistance to compression ignition ...so it wont make any difference unless you are boosted or have the advanced timing to compinsate for it.

 

Where does it "Recommend 87"? It says it can use 87, but that performance would be degraded. Like alleycat said, GM recommends at least 91 for best performance

 

the higher the octane does not mean more performance ...it is the resistance to pre ignition (knock) you dont get a more powerfull explosion. you get resistance to compression ignition.

Using the 94 octane is pointless as our compression (more compression more heat) is not that high thefore we dont need worry about pre ignition. Untill you add more boost to raise the compression in the cylinder thereby rasing the heat and the chance for pre ignition (knock)

 

Yes it does, higher octane means you can run more ignition timing without detination.

More ignition timing = more power.

So yes higher octane means more power as long as your PCM is setup to handle it. Thats why they sell hand held tuners that are setup for 93 octane. In a stock car setup to run with 87 your right added 93 isn't going to add more power.

 

as a side note I use 89 octane fuel to eliminate the possibility of Knock at current boost settings without paying the premium ...for premium or above

 

I mentioned that in my first post ...however most people will not have the PCM Setup that way and in this scenario it has no bearing as 05vicredSS has not advanced his timing

 

The SS comes from the factory tuned for higher octane gas, so yeah he can run it and get better performance.....do you honestly think that Chevy would market this as a performance car, then set it from the factory to run a minimal timing...I think not.

 

The LSJ PCM is setup to work exactly the way I described advancing the timing until it knocks. And since he has a SS/SC he would get more power by running 91 octane. If you don't belive me just check your owners manual it says the same thing in there.

 

Thats what I meant....it can adjust timing....thanks Zinner

 

but he is talking about 93 octane ...which will not help him at all performance wise

 

Did you forget what we are talking about? He wants to know if the switch from 87 to 93 octane will yield a better MPG/Performance gain.

Yes 93 octane will get much better performance than 87. By using 87 his PCM has taken ignition timing back...if he switches to 93, his PCM will compensate and advance timing which will give him better performance.

93= Higher price/Higher Performance possibly better MPG, but probably marginal at best.
87= Lower Price/Retarded timing-performance

 

yes I did get off topic a bit.

he will get marginaly better performance but it is probobly not worth the extra money to go above 91.

as for fuel economy he may or may not get better comsumption ..I get the best consumption with 89 then 91 then 87 (dealer fill up) then 94 (drove it allot harder)

 

Here gas is sold as 87, 89, and 93 octane. So which would you rather run, the 89 ir 93?

 

89 for daily driving becasue it would be chaper ..and I dont race 100% of the time .. if I was heading to the track I would hit up the 93 for the extra coupple of horses

 

**** fill up at the track and run 104

but dont go over 104 with a catalytic converter. Your car will blow to ****.

 

I can get 91 or 93 at the same price, so of course 93...I ran 91 for two months then switched to 93 when I found it, and yes I could notice a difference.

If you can find it for the same price, then put in 93......personally, I wouldn't go 89 when it might cost you 1.20 more to get 91 or 93 for the whole tank.

And if you want to just fill up on race day, get 93 then maybe cut it with some toluene....can be found at most paint stores. Do a search if you don't know what it is.

 

Partially true.

The PCM will advance timing up to the limit GM gave to it as long as it does not hear any knock. That limit was calculated using 91 Octane fuel (highest octane fuel readily available in the US). The PCM will not advance the timing past that point if you use 93 Octane or 100 Octane or 104 Octane. This is using the stock program and stock boost levels obviously.

 

It's the same here (except at Sonoco where you can get 87, 89, 93, and 94). For me personally I always run 93. I ran 89 in it once because the station I stopped at was out of 93 and yes, I noticed a difference plus got slightly worse fuel mileage on 93.

Like a lot of things, it's personal preference. The car is tuned to run on 91 octane so I always make sure I put at least that in it (though I've never seen 91 octane around here). The biggest difference in price I've ever seen between 89 and 93 is $.10, some places it's only $.08. At the most if your tank was absolutely bone dry and you had to put the full 13 gallons in, it's going to cost you a whole $1.30 more per fill up.

To me the extra performance and better mileage is well worth the difference in price.

 

I feel the same way. It's kind of funny to me that someone would pay extra to have a supercharged car but then not want to pay the extra $1.50 per tank on gas to the the maximum potential out of the engine.

 

Yes.. you get a tuner car.. and then rob yourself of some horsepower by using low grade gas. Then you spend money on a CAI to bring it up to the power they would have already had just by using premium on the car stock! That's an exaggeration, but the anaology works.

 

Now the question I have is, who has the best grade of 93? Im guessing Shell being one of them?