i have an 04 monte SS with the supercharger. it is stock with approximately 108000 miles. A local gas station just started selling 93 octane and i was wondering even though in the manual it says 91 octane or higher,if it would benefit at all to use the 93 octane instead of 91. i was reading information and i got mixed opinons on yes or no, some said if you have it specifically tuned for 93 then it would benefit and some answers said it would benefit either way and not having the tune would leave it available to use either 91 or 93 without any engine knocking. any answers on the benefits that it would gain and what they are if any would be greatly appreciated. and not sure if it matters but i live in southwest missouri so if location or elevation matters theres the info.

 

My suggestion would be to use 93. Your manual says 91 or higher because not all stations carry 93 (some by me do and some don't) so if you don't have 93 available, you can get by with 91 but your car would benefit more from running 93.

You may feel a TAD more power - and you'll get better MPGs because you'll have lower pre-ignition rates.

 

Stick with "top tier" 91 octane or better.
Read this:
Top Tier Gasoline

Saving a penny or 2 on gas can and will cost you a mile a gallon or more. I've proven that time and time again, and with the cost of gas, which is cheaper, cheap gas or better gas mileage and less engine and fuel system problems from a higher quality, but more expensive by a penny or 2 gas?

Unless your engine has mods, 91 should be OK, but I have problems because of too extreme mods running 93 octane, let alone 92 octane. I wouldn't even think of 91, but then, I've never seen that around here. It's either 92 or 93.

 

i use 93 octane in my n/a monte carlo seems to get better mpg.

 

Unless you are tuned for it, it's a waste. I have a topswapped car, running higher compression then you, with headers, ported everything, and a HAI. I get no knock on 89 octane. I think you will be fine.

 

In your case that's a bad idea - unless you tune your spark tables. Your cars sparking is tuned for 87 octane - if you don't increase the spark you'll just be passing unburnt fuel through your system, which will actually dirty things up and plug your catalytic converter.

It won't help your MPG either because the car can only spark the fuel so fast - if the fuel is more rich (like 93) it won't all ignite before going through.

You can never GAIN mpgs by running higher gas - you can only loose it by using a lower octane grade - if you use a cheaper grade the car will pre-ignite (the gas is cheaper, requiring less spark to burn it, it also has less potential energy) but since the car still takes fuel in at the same rate regardless of grade, the cheap grade has already been burnt through before the next burst of gas comes in - which is where you get knock and loose MPG because it takes more gas to get power.

How long have you been running 93? You may want to change your fuel filter and run SeaFoam through your gas tank and through your brake booster line to clean all that unburnt crap out of your system.

 

Basically what it boils down to is:
87-93 is how your engine sparks. You need so much energy to have your engine to make the most of a higher octane.
If you use higher than what is required you simply are not using all of the gas.
The reason most people see MPG improvements is the additives.
Read the ad's we will clean your engine with our detergents but they only add them to their highest octane.
Does it hurt? No
Do you use all of it? No.
Does it make you feel better using name brand oil vs "generic"? Peace of mind.
Bottom line is use 91+ and you are fine.

 

I have my car tuned to run 91. It has made a noticeable difference in mpg's and performance.