What kinda octane should I be throwing in my car??

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1991 Firebird Formula, 305, TPI, Auto...stock till I get some money!!!
Former owner of an 88 2.8 Firebird....RIP

 

a mildly modified 305 TPI is fun as **** to drive. it tears it up and never breaks when you beat it. i bet you feel like you were standing still drivin the 2.8 now that youv'e upgraded to 5.0 power. welcome to a real third gen experience. think your chick costs you a lot of money!!!!!!!!!!!

 

Hell no, my woman pays her own way.....we're all equals ya know!!

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1991 Firebird Formula, 305, TPI, Auto...stock till I get some money!!!
Former owner of an 88 2.8 Firebird....RIP

 

The lowest octane you can get away with, without the engine pinging. On yours, 87 octane is fine. But if you have lots of money and like making the Arabs rich, buy 94 by all means. Any performance gains noticed will be due to the placebo effect.

 

Okay, thanks Glen...hey your from the wild wild west of the great north too.....maybe you can help me with my other question. Do you know if anyone in our province sells Magnaflow exhaust products????

Noone seems to wanna answer on the exhaust board!!

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1991 Firebird Formula, 305, TPI, Auto...stock till I get some money!!!
Former owner of an 88 2.8 Firebird....RIP

 

I always thought that in order to get the power out of the higher octane fuel, the compression had to be a little higher.

I have a question of my own, what is the highest compression that you could have to still run 87, i am just a student and i don't have the most funding in the world and i need to save up for college.

any help will be greatly appreciated.

 

Just don't try to advance your timing if you're running camel **** 87 octane gas. My friend, who drives an 88 T/A, learned this the hard way.... his car drove like **** after filling up with 87, pinging all the way down the road.

Performance car, performance gas. I won't run anything but 93.



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91 Trans Am WS6
Bright White
5.0 TPI auto
Flowmaster 3" 2 chamber catback
Trans Go shiftkit
2000 stall converter

supposed 'peanut cammed' car (yeah, right)

Built on Wednesday

 

87 octane fuel is not acceptable in a tuned port 305. A 305 TPI has 9.5:1 compression, which likes 92 octane fuel. You can probably run 87 octane fuel in the engine but the knock sensor is going to retard timing if you do it. You will not see maximium performance with the 87 octane fuel.

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1988 Formula 5L/5sp 3.45 gears, SLP cold air kit, MAS gutted, TPIS air foil, TPIS AFPR, MAC headers, Mac under drive pulleys, MAC cat back, Relocated MAT.
Best ET street tires 13.85
Best 60 FT street tires 1.930
Best MPH street tires 99.29

 

Unless you are changing you compression ratio or you are trying to run with advanced timing you will not notice any difference in power or pinging our 3rd gen cars were desigined to run on 87 octane

 

Mr J has a valid point about ignition timing, whether by increasing the base timing or by adding a chip. Prior to my mods, which included a chip, I could easily run 87 without any noticeable difference in performance.

Since I have made my mods and added my chip, I do get a fair amount of "inaudible knock" and a decrease in performance. No pinging mind you. The "inaudible knock" is detected by my Diacom readings which causes the knock retard to kick in, this results in poorer performance.

It runs fine on 89, but I have observed that my chip will not put quite as much advance as it does with 92 or 94. From a performance perspective, there is no noticeable difference, though the engine does feel "crisper"... I attribute this to the placebo effect.

Regarding the Magnaflow exhaust, no, I do not know if anyone sells it. I find that most muffler shops don't want to be bothered with anything than their "replacement muffler/exhaust". But do look around and there are some muffler shops that are willing to get you a good exhaust system. Try Mopac in Surrey/Delta. They can get most anything and will install virtually anything for you, if you want them to.

Regarding Ace's question, while compression ratio is definitely a factor, so is your ignition timing as Mr J pointed out. If your compression ratio is not too high (say above 9.5-9.75:1) you can retard your base timing a bit to run regular octane. Remember that fuel injected cars and aluminum heads can tolerate higher compressions on a given grade of gas than a carb/iron head engine. But ignition timing is a very important factor to always consider when determining the lowest grade of gas you can safely use.

[This message has been edited by Glenn91L98GTA (edited November 02, 2000).]

 

Yeah, I live right out here in Surrey, so Ill check with Mopac, even though Ive heard that their installation is a lttle sketchy.

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1991 Firebird Formula, 305, TPI, Auto...stock till I get some money!!!
Former owner of an 88 2.8 Firebird....RIP

 

What about octane boosters? with the fuel prices being so high, can a octane booster be added to 87 octane to get anywhere 93 octane, and still save money? I have see boosters out there that where about 2 buck(i think the name is 104 ?) a bottle and they would treat 2 tanks of fuel.

if I could some what save money i would do this. but now i have absolutly no clue about octane boosters.

if you can help it would be greatly appreciated

 

I know I initially asked this question a while ago, but Im gonna follow up!

ive tanked up twice since the initial post and both times I filled up with 92 octane. The car seems to be running alot smoother and cleaner, no noticable power gains though!

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1991 Firebird Formula, 305, TPI, Auto...stock till I get some money!!!
Former owner of an 88 2.8 Firebird....RIP

 

You have only used 2 tanks of gas in all that timme? I burn more gas than a marathon runner burns calories.

 

the oil companies(though not necessarily the arabs) will get richer regardless of whether I use 87 or 94. if i decide to run 87 for the sake of economy(like economy matters when you are driving a heavy car with a 350 and a slush box) I will be such an insignificant blip that the oil companies wouldn't evem notice. and if I convinced a million people to do the same thing, I'm pretty sure all the oil companies would raise their prices to make up the "loss".

the owner's manual recommends 91 and the filler cap says "premium only". do ya suppose Chevy was only offering a suggestion or perhaps were they trying to make the arabs richer?

the arab argument falls flat on me. at present Alberta supplies over 25% of Canada's oil, this number is predicted to exceed 60% by 2012. at present only about 5% of our oil comes from "arab" countries. When you add the reserves in: the oil sands, Beaufort and Hibernia, Canada's reserves dwarf the Gulf. One day our southern neighbour will depend on us for more than real beer and wierd pronunciations.

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He who hesitates,... is lost!

 

I can only get 92 octane here in CA, but I use NOS octane boost at the track. When they say 3 or 5 or 7 points of octane its misleading. What you really get is .3 or .5 or .7 boost. So if you pour it in a tank of 87 octane, you'll be lucky to get 87.5 octane. And it costs $12 for a bottle of the race formula here.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

Thanks, now that I have more info on boosters, i don't think that I will buy any.

I find that putting 93 in my car isn't all that bad. If I don't plant my foot into it it gets great fuel economy.
and for my tank it is only about $2.00 more than 87.

thanks again, and keep beating those rice burners

 

One other note on octane boosters: some of them have additives(like lead) which can be very unfriendly to your cat and O2 sensor. How much are ya saving if you shorten the life of these components?

If yer that worried about saving a few bucks at the pumps, get a Camry and impress your parents with your appearance of settling down and acting responsible. Save your f-bod for those moments when you feel like being a rebel.

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He who hesitates,... is lost!

 

A fried alternator kept me off the roads for a while, thats why its only 2 tanks as opposed to the usual 4 in that time period!

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1991 Firebird Formula, 305, TPI, Auto...stock till I get some money!!!
Former owner of an 88 2.8 Firebird....RIP

 

The highest octane you can get.
The additive package is different, and amount of ash generated.
You'll always have an engine last longer with the higher octanes, when **Tuned** correctly.
You'll more then break in long term tunning the higher octanes. I just base this on 30 years of working on hot street, and race cars

 

I run 87 octane in my car with 9.5/1 compression ratio. I get better gas mileage with the 87 vs. 93. I don't pick up any knock counts with it (according to my EASE scantool). My timing advance is set at 10 deg.

Back when I first got my car ('90), and it was a measley 5.7 with no mods, I made several trips from Dayton, OH to Florida. On 2 of these trips, I tracked my gas mileage with different octane levels of gas. I always got better MPG with 87 than I did with premiums (92 - 94). Averaged about 25 mpg with the 87 vs 22 - 23 with higher octane. Had a best of 27.5 mpg with 87.

I've always heard to run the lowest octane that you can get by with that doesn't cause detonation.

Just my .01999999.

Sparks a flyin.

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1989 L98 IROCZ, Bored .030 over,400 Crank,Dart PRO 1 Heads 200cc intake,ZZ3/ZZ4 Cam,Crane 1.6 RR,Edelbrock 3860 Hiflo TPI Manifold, AS&M LTRs, Edelbrock 58MM TB, Ported Plenum, TCI Reverse Pat Man Valve Body, SVO 24# injectors,TCI Streetfight Stall Converter, 3.23 Gears on Auburn Pro Posi, Some Suspension Mods