OK, lets say im running 87 octane in my cavalier. And im getting bad gas mileage. If i have some upgrades, would I have better luck with the 87, or 91 octane?
Thanks..
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1963 Buick LeSabre, 401 Nail-Head, SOON TO BE TURBO POWERED
The octane rating is basically how well it will resist knock, or pre detonation. So its not really going to help fuel economy.

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There are also some speculations about it actually being bad for your motor, due to the slower burning process of high octane gas, some say it will leave carbon depostites in your motor...but we wont get on this argument, it could go for years.
going to a higher octane wont help any, and niether will avoiding ethanol blended gas. if the stuff was bad for your engine, they wouldnt blend it.
a car not set up to opperate on a higher octane wont see any bennefits of going to one.
Injection is nice but id rather be BLOWN!
I see so many different octane ratings. 85, 87, 89, 90, 91, 92.....and im not 100% sure but a 93? I was going to put in the 90 w/ 10% ethenol but used 87 instead.
I always keep my tank filled with 89. Then usually every 2/3 months or so, I use this fuel additive cleaner that works really well. My car usually gets between 230-260 miles a tank this way.
I always used 93 or 94 when I could get it, but I used that to prevent detonation from the nitrous.
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the only time i use higher octane is when im planning on using nitrous

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i was thinking that 89 octane gas would be better for the z24 because the compression is sorta high.
aint that high

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Heh. maybe i'm crazy but it seems like i get more power with 91 octane rather than 89 or 87. But i also have all aftermarket ignition parts too.. that could have something to do with it.

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Hi guys. I work for the oil company's, when they transport gas in the various pipelines the grades are seperated, but within each grade they are all the same until it gets to the local tank farm. EX: If Shell puts regular 87 in to be shipped, then Texaco puts in 87
to be shipped they are ran in the same batch. When it get to where it's going, each shipper gets it's volume, but it may not be the same gas they put in to start with. (Fungible .vs. Non-Fungible) The only brand/grade that's kept totally seperate is Amaco Ultimate. (The Best) After the gas gets to the local storage tanks for each brand, then the additive pack is mixed in. Unless your running boost, or nitrous 87 should be just fine for any j-body. I'd reccomend staying away from the ethanol/methanol because it eats up rubber seals & stuff. Now understand 87 and 89 are not always 87 & 89. That's the minimum R + M, if a shipper ships 93 and it somehow gets a little Kero or Diesel it will be downgraded to the next grade below it. Thus if you buy 89, it might be 93 with a little "product contamination" and was downgraded. Same goes for 87.
I run use 94 octane everyday and I find it makes a HUGE difference. If I go to another station and just get 91, there is a difference. I've noticed that higher octane increases power, makes for better starting and it keeps the injectors cleaner than regular gas will. Also, Higher octane burns better so you get a little bit better fuel mileage (not a whole lot). Not all the gas is burned when it ignites and that causes power loss. When higher octane gas burns, there is less less left over "wasted" gas.
But bottom line I have tried regular, super and the ultra (94) and I find their is a BIG difference between the 3. I stick to Ultra at all times. I find its worth it. But im not running forced air or nitrous so i need all the extra kicks i can get lol
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there was an interesting artical in a european mag. called EVO. it was about this subject. they went through a long testing to see if the higher octane fuel would be the best. they have way higher fuel prices so this is helpful to them. they found out to things.
#1. the octane ratings did make a differance. (they dynoed each fuel.) and the brands made a difference as well.
#2. fuel breaks down after awhile and so it is best to find a local station that is busy, that way you know the fuel will be the freshest.
this was all done in the U.K. so things might be different here in N.A. but i doubt it would be that different.
Exodus 259 wrote:I always keep my tank filled with 89. Then usually every 2/3 months or so, I use this fuel additive cleaner that works really well. My car usually gets between 230-260 miles a tank this way.
I hope you are driving in city traffic 100% of the time, if not that sucks. I drive from my place to downtown Washington D.C. everyday, for a total of 45 miles each way. I sit in traffic coming home and I average about 70-75 most of the time(when I am not in traffic). I am pretty heavy on the pedal and I still get 31-34mpgs. I fill up before I hit the fuel light, yesterday I put 11.7 gallons in and went 372 miles and that came out to 31.7mpgs.
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2010 Ford Explorer
2006 Ford Ranger
2004 Chevy Cavalier
we can debate about this until the planet runs out of gas. id say just stick with the regualer

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Oh yeah, I use 87 to. Anything more without boost or nitrous or high compression is a waste on a J. Some people claim more power, its just

to me and the ones that say it increased there mileage by 1mpg, thats great and you pay at least .10 more a gallon for it. Just not worth it.
2012 HD VRSCF
2010 Ford Explorer
2006 Ford Ranger
2004 Chevy Cavalier
It's all dependent on the mods. On my Cavalier, it's pretty much stock, I use 89 because in Iowa, 87 is more expensive and so is 91. But on my Laser, I run nothing less than 91 and even then I have the engine detuned. When I go to the strip I run C16, which is EXPENSIVE!!!
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My car seems to run well with 91, but it really loves when I can get some Ultra 94 in there. So I do as often as I can. Call BS if you like, but I can see and feel the difference.
Truck gets 87.

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Your car as in the GTP? If so, sure it does, its boosted.
2012 HD VRSCF
2010 Ford Explorer
2006 Ford Ranger
2004 Chevy Cavalier
I want to see some dyno sheet on a J BODY nearly stock... or I'll have to say like a lot of people already said
Shifted wrote:Higher octane = slower burning flame. The Eco is calibrated for an 87 octane fuel, so unless you are FI, higher octane is a waste of money.
Octane simply slows down the flame front in the combustion chamber, producing a "softer" explosion, which is why FI cars use it, to reduce the chance of knock or reduce the harsh conditions due to running lean.
This is what really happen, this is what I was gonna wrote but Shifted had a clearer answer. And by the way a butt dyno worth nothing....
I have been talking to a guy on line who claims he has been reading sensor data while running the different grades of fuel. He says with the higher grade fuel he gets more timing advance. He is NA as well. Thought that was interesting.
The pcm don't have the choice to play with the timing to avoid knocking. It will always try to run the safest possible