I have A 91'Bird, stock 305TBI> been running 93octane, but after reading hear and there I've picked up that lower octane fuel is better( for a stock 305 anyways). So what is the correct answer? Throttle response doesn't seem as good as it could! COMPLETE tune up has been done within last month. It seems like the low end torque sucks!!! My wife's 2002Grand Am GT (V6-3.4liter ram air) could whip my Bird off the line!! REGULAR OR 93OCTANE ????? Thank you- MIKE

Premium fuel is only worth the price if your high compression engine pings on lower octane fuel. Your 305 should run fine on mid-grade or even regular.

It should run good with either I've only had to run 93 on two vehicles I've ever owned . The first was a Chevette that I put Bosch Platinum plugs in and my '85 Ironhead Sportster which is heavily moded . All my cars I've owned ran good on 87 but ran better on 93 and two of them one being my Firebird and the second being a 87Thunderbird Turbo Coupe I've run 93 mixed with 2or3 gallons of 110 with no problems .The Thunderbird seen 200+mph and the Firebird has seen around 140-160mph .

From reading other post I picked up that on some cars that the combustion is not as good as it could be by using higher octane gas. Depending on timing and set up. That the cumbustion is actually better on a lower grade fuel Better cumbustion, better efficiancy = more power.

Very true .

Running higher octane fuel than your car requires does nothing. You might as well burn your money. The engine can't tell the difference. It always gets me when people claim that their car "runs better" on premium. I think it's psychological (barring the new cars that recommend premium and retard the timing when regular fuel is used which actually does decrease performance) or the gas station you get your regular from is giving you bad gas.

Higher octane will prevent pre-ignition, and if you aren't running a higher compression ratio, you aren't even using the higher octane's ability to handle higher temperatures without igniting.

My post when I said my car ran better with93 was referring to the Thunderbird which had a switch to run high octane fuel and when I ran 93 in my Firebird the timeing was advanced . Sorry I didn't include that in my first post .

Will the higher octane gas (that I don't need) affect my low end torque? My bird runs great, don't get me wrong... Just not much "ooompf" when I get throttle happy, Not like the response I get driving the wifes car(specs 1st post)

If it's not burning right, everything is affected.

No it won't. You should see the same performance out of your motor using regular as compared to premium.

Premium does not burn "better". It simply prevents burn/ignition until a higher temperature is reached.

I do know that imports like EVOs etc can gain drastic performance from a high octane fuel. But it's not directly from the fuel. It's because they are changing the tune of the engine, which could not be run on a tank of regular gas. A lot of guys will run it while they are at the track.

Hope that helps.

Gonna switch back to Regular fuel. Don't think it will matter. I guess I was hoping I could Blame the fuel, but After 22 years of driving many different cars I'm getting the sinking feeling I am noticeing the slow progresion of the dreaded >>"trani Slippage"<<

I run 89 octane.. When I run the 86 the exhaust smells weird. Could've been that winter gas, too.

Where the hell do you guys get 93 octane fuel?

The chevron by my house has either 91 or 92 as it's highest.

My Sunoco up the street sells 94 at $1.02 a litre. The speed shop a block away sells 114, and 130 by the gallon.

Yeah, I also run 94 out of the pump - Chevron!

Of course, I'm about 10.5:1 so it's more of a requirement for me. I'm going to TRY backing down to 91 and see what happens.

I'll have to read more into it, but from what I understand, for a given volume of fuel (be it 1cc or 1 gallon) there is 'x' amount of combustible material in it. Jacking up the octane (which is a knock suppressive material [call it 'y']) reduces that 'x' by the volume of 'y'. So, therefore you actually can hurt performance by going to a higher octane when it's not required!

It's the same principal as motor oil. Straight 30W oil has more lubrication than 0-50 would if they made that in a Dino oil (I'm NOT talking synthetics here). The additives to make up a multi weight oil reduce the actual mass of lubricant in the oil.

wtf? i've never even heard of 114 or 130, that's crazy!

i've never even seen a sunoco fuel station over here in california.

Isn't Canadas gas rated different ?

Negative. It's all RON/MON.

Europe is rated differently, so there numbers come out much higher.

Thats what I thought .

I use to work at a small airport for small planes. hell guys were pulling up to the pump and putting in 130 octane av gas into thier camaros and other cars and motorcycles.

I would'nt do it. myself. I run higher octane on vehicles with higher milage and that have carbon in the combustion chambers which gave me some issues on hot days with pre ignition. I run the higher octane in my camaro cuz I have the timing advanced.

Also there is some stuff with opening up the gaps in the plugs and getting longer spark times and some of my buds use the higher octane as well.

Then a higher compression engine needs the higher octane as well, octane is a measurement of resistance to self ignition more or less.

and nope never noticed a difference in my motorcycles or various cars i have had.

One time I was running low on my 87 octane at the track so I got a couple gallons of 111 octane and ran that, and what do ya know, the car spit off the same 1/4-mile run as the ones before it. Seen this done on an engine dyno test. As long as you can run the proper amount of timing with a given fuel, more octane does little or possibly hurt performance.

isn't the US (and CAN) rating called AKI (anti knock index) which calculates (RON+MON)/2?

over here we have RON, 95 RON is about 89-90 AKI. in austria most pumps stopped selling 91 RON (87 or so aki) recently, most cars require 95 anyways.

anyways, i think 93 is overkill unless you're running a lot of boost or compression.. it won't do anything unless your ecm is tuned for it.

Yeah it's (R+M)/2. You'll see that on every pump you pull up to.

It's the average between a lab test and an actual motor test.

Needless to say but if your car isn't tuned to run on 93 or higher octane you will not see a difference in power .

My buddy put that av gas in his car, and took it to the dyno.....the dyno guy kicked him off, told him to empty the tank and come back with good gas.....he said that av gas contains anti-freeze for high altitude, which might be true......but the dyno chart was Everywhere....bouncing all over the place, up and down through the whole rpm band....he put normal gas in it, and re-dynoed it, ran fine, got a good dyno sheet.
The rule I go by is.....'you only need enough octane to keep motor from pinging or pre-detination...'

Hey 91interceptorZ why don't you tell him to just put a 300 shot to it .

Yea I got a couple stations with 93 octane in my area but not worth it so I run regular 87. I had a car with a dieseling problem and running 93 through it from time to time would stop it .

hey....that'll work....you'll need the octane with that!!! That's funny....

I thought you would get a kick out of that .

I bumped the timing up 4* so I just run 93 for the hell of it.

After running 89 for a week, instead of 93. Car cranks up great in the A.M. still and the throttle seems more repsonsive >>> No more 93 for me! No need for 93 with a stock set up... Car runs great!

Been having some light pinging under load lately. I have been running 89 for a while now and switched to 93 last night. Didn't feel too much of a difference really. It did get rid of the pings tho.Then i advanced the timing two degrees for the 93 octane. Felt ok, smoother overall, but it really felt like i had more torque with 89 and the lower timing i was running.

I ran Regular 89 in mine for a while.But the guy that programmed my chip in my car set it to have Premium? Im not sure if thats true but thats what he told me. When i ran regular before the car ran great,it just had a miss at fast take off. And it seemed to want to die at points. I dont know if or why it would have any effect but i ran 93 octane and the car Doesnt miss anymore and it seems WAY more responsive. Who knows

dont need it. but I do recomend bumping up your timing to 6* BTDC