There was a member who has made me wanna switch the type of fuel to use. I use regular unleaded just because it's cheap, and most importantly, it gets me from point A to point B. So from your personal experience, lets hear from you guys on what you think is best for our TPI. So who's willing to participate? What do you use?

1. Regular Unleaded 85-88

2. Mid-Grade 88-90

3. Premium 90 and up

 

Here is an explanation of fuel and octane that I found here at http://theserviceadvisor.com/octane.htm

The type of gasoline to use is one of the most misunderstood areas of vehicle ownership. I am going to offer some ideas that I hope will save you a few bucks on gasoline.
The first rule of thumb is that higher octane gasoline is not necessarily better for your vehicle.
WHAT IS OCTANE RATING?
Octane, by definition, is the resistance to burn or detonation. The higher the rating, the slower the burn when ignited during the compression burn cycle of the piston. The higher octane allows for better control of burning for high compression engines. So we want to match the correct octane rating of the gasoline to the engine design to ensure complete burning of the gasoline by the engine for maximum fuel economy and clean emissions.
I THOUGHT GASOLINE WITH HIGHER OCTANE REDUCED ENGINE KNOCK?
It did in older engines using carburetors to regulate air/gas mix They cannot as accurately regulate the air/fuel mix going into the engine as a computerized fuel injector. Carburetors need adjustment, as a part of regular maintenance, to keep the air/fuel mix as accurate as possible. So many times, these adjustments were not made regularly causing too much fuel to be mixed with the air. When this happened the gasoline would not burn completely soaking into carbon deposits. This would cause a premature ignition of the gasoline due to the intense heat in the engine cylinder creating "engine knock." When this happened, people would change to the higher octane/slower burning gasoline to resist the premature burn, thus minimizing the knocking problem. And it worked. Good solution.
However, since the middle to late 80’s, engines are designed to use fuel injectors with computers to accurately control the air/fuel mix under all types of temperature and environment concerns. However the accuracy of the fuel injectors and computers is based on using the recommended gasoline for that engine.
Most cars are designed to burn regular unleaded fuels with an octane rating of 87. If the vehicle needs a higher octane rating of 89-93, there is documentation in the owner’s manual, as well as possibly under the fuel gauge and by the fuel fill hole. Usually you will see this rating for high performance engines only.

 

Unless your car has a higher compression than the stock engine you should most likely be using 87 octane fuel in your thirdgen. I can't speak to Firehawk and Turbo Trans Ams but the L98 and LB9 cars run fine on 87 octane gas.

 

Dont know if this is just my car or what, but the one time i put 87 in, it was acting strange, and when i switched back to my 90 + it acted normal again...

Might just be my car though

 

I made this thread because another member said that in our owners manual, it states something like if we use regular fuel (87) that we run the risk of detonation. Here is his quotes ; "If you read your owner's manual carefully, you should find the note on fuel quality. It says sometning like: "your vehicle can operate on 87 octane however you may notice a decrease in performance and fuel economy". Todays oxigenated fuels(10% ethanol) will only exacerbate this problem."

From what I read at a GM source, our engines were built to run on regular unleaded (87) for optimum performance.

 

I remember my 1987 owner's manual as stating that the vehicle was designed to use regular 87 octane fuel. Now my GTO and Firehawk owner's manuals stated something along the lines of the quote from your post about 87 octane fuel potentially working, but not well. 93 or better octane fuel was recommended.

 

it all comes down to the timing, and the type of Chip you got in your computer... in my 87 with a Hypertech chip, it would ping upon acceleration...once I switched to 91 it went away, or at least I never noticed it again.. .but of course the Chip instructions stated higher octane would be needed....

 

I run 93 in my car since I have initial timing set @ 12*.
I can run 87 but if it is warm outside and and I am in a higher gear at low rpm then I get a little detonation.
At stock 6* it runs decent with 87.

 

I run 87 & have tried 92 octane, calculating mpg on both. My car ran no better with higher octanes nor did my mpg increase, so I switched back to running 87. And my wallet is heavier now than when I was running 92.

 

I dont know who wrote that, but they are/were apparently completely incompetent.

The carb had little to nothing to do with it. I guess this joker has never heard of compression, swirl, quench distance, chamber design, port design, etc etc etc etc. Most older cars had fairly high compression that were DESIGNED to run on high octane fuels. Then the octane numbers went down, and a bunch of those cars started to run like crap... because... the lack of octane.

I've always used 87 octane in my cars, its never been an issue. Just dont fall into that trap that some people profess that higher octane=more power. There is no more energy in that fuel than any other.

 

depending on the application, higher octane does = more power, on boosted cars.

 

Try reading all of what I wrote next time, namely "There is no more energy in that fuel than any other." Extracting as much of it as possible is an entirely separate discussion.

 

Ok guys, lets keep it clean, no arguing. So it all comes down to timing and user preference.

 

It wasn't me.

 

Hello Chevy86 IROC-Z!!

I run 94 Octane, only because my owners manual says so, with my TPI set up!!

You can however run any Octane that you want, saves you $$$, but you will run the risk of creating spark knock (detonation)!!

The decrease in performance that the owners manual says that you will experience, comes from the fact that the engine will most likely start to ping, which will be picked up by the knock sensor, which will relay this to the ECU, which will retard your spark timing, resulting in decreased performance!!!

All this is for a completely stock engine, performance mods are another whole can of worms in relation to Octane requirements!!



P.S. You may not think that your engine has spark knock, but just because you can't hear it doesn't mean that the sensor can't!!

 

 

You migt wanna reread your owners manual. I seriously doubt a 87 was "require" 94. My 1987 Pontiac Trans Am 350 TPI is perfectly happy on 87.

 

its more than timing and user preference.
a motor can have 9.5 compression and run perfectly fine off 87.
like max said, the design of the motor has a lot to do with what grade of fuel the motor needs. also, gearing, vehicle weight, and how its used comes into play.

in cool weather i run 87. in the summer i run 91~93.
at times in warmer temps my car pings pretty bad on 87.
at about 50 MPH in fourth gear with the TCC locked, my motor only spins around 11~1200 RPM.
even with 91+ it pings under light acceleration in the 50~60 MPH range.
with the TCC unlocked, it doesn't ping.
i know the quench isn't right and gearing certainly isn't optimal.
if i had the quench right, maybe i could tune the ping out, but again with my
gearing, i doubt it.

 

You will never, ever, get more power per volume of higher octane gas, compared to a lower octane. Technically, it CAN = more power, but that is due to the gasoline's characteristic of being able to not detonate early when there are high cylinder pressures present. "Octane" is simply a mix of hydrogen, and carbon. Carbon is useless when it comes to making power, it just resists detonation more. (Which plays a major role in actually making power, but it contains no energy it's self) With that said, more carbon = less energy per volume.

Sure, if you're considerably high boost on a built 383 stroker, race fuel will aid you in making more power by resisting detonation due to high cylinder pressure, but it has considerably less energy per volume. Although, there are elements in the carbon group that are flammable, which do contain high amounts of energy. The high carbon content of Diesel fuel is actually why they typically run 17+:1 compression even on boosted applications. My buddy's 12 valve Cummins runs well over 20 PSI (However, you can accelerate faster with a bicycle) with a stock turbo, stock engine, every single engine component is stock.

 

Hello Stephen!!

Your right, it doesn't say "require", but the owners manual, on page 2-6 under Fuel Requirements states: "Your engine is designed to operate on premium grade unleaded fuel. However, with the electronic spark control system, you may use regular unleaded fuel at slightly reduced acceleration performance."

That to me says to use premium, sure you can use the other crap, but only the best, for the best I say!!!

 

LOL. I absolutely love Third Gens, and always will, but I'm sorry.. The best? Is that why a 305 will get spanked by a simple old SOHC V6 Honda Accord?

 

Hello Shadow Z!!

The "best" was in referrence to the make/model, not the ability of the car!!

Technology can change the outcome of things over time, SOHC V6 Honda Accord's included!!

 

Yup. I agree. Back in the late 80's, the IROC-Z was one of the fastest cars around (for the general public as a street legal car). Now a days technology and power packages have increased. I bet a 86 V6 Accord, would not be able to, in your words "SPANK," the 86 IROC. You must remember that times change and with that, there are differences in power. I hate it when people tell me that their Mustang (2009), can beat my IROC. I tell em that I can give em a run for their money knowing very well that I may not be able to beat em. Now guys, .

 

Honestly, it's kind of sad, because a 1986 Accord was a 17 second car. What'd most 305 IROC's run, mid 15's? They were sort of quick for the 80's, but still lacking a whole bunch.

It's just the type of car that you really have to love, and have a desire to own. I loved IROC's ever since seeing Macgyver steal a yellow '85 in one of the 1985 episodes, when the IROC was practically the hottest new car around.

 

Hello All!!

"It's just the type of car that you really have to love, and have a desire to own." as quoted from Shadow Z!!

That's why I have three of them!!

1987 IROC-Z 305 TPI 5 speed White
1987 Z-28 305 TPI 5 speed Blue
1989 IROC-Z 305 TPI 700R4 Red

The Heartbeat of America lives at my house!!!



For Shadow Z, they all run on 94 octane!!

 

That's your problem, bud. Not mine. The extra carbon in 93/94 octane will simply just not fully burn with a stock tune. I hope you're running your timing within a few degrees of TDC, or else you're just killing your engine.

With a stock tune and 94 octane, you're wasting your money, depositing a sh!tload of unburnt carbon on your valves, costing yourself power, and decreasing your fuel economy.

I love the people who run 93/94 octane on what are probably 100% stock engines, just because they think it sounds cool, makes it a hotrod! Yeeeeeeehaw dat 94 octane gimme meh engine some PEP! No, you're costing yourself power. By all means though, keep wasting money, and polluting more than you have to.

"Currently man is responsible for around half of total hydrogen emissions"

I hope I don't live near you. Octane is a hydrocarbon if you did not know.

 

Hello Shadow Z!!

A little touchy with the octane, are we???

For me it's, the "feel" of the car, it feels smoother, it performs great, and every year it passes it's emission test, so I don't get the hydrocarbon slant that your on!!

The emissions dudes set a standard, and I keep beating it, so I'm good to go!! I'm as "green" as I'm going to be!!



I've tried other octane ratings, and they just don't have the same "feel", call it psychological, or whatever, it works for me, besides, they make the stuff to sell, and someone has to buy it!!

 

Not touchy, just talking a bit of common sense. It's not so common these days.

BRB! I'm gonna go fill up my IROC with some 90/10 nitromethane/methanol mix from a top fuel dragster. I believe the stuff costs around $50 per gallon, but it'll feel like I can do over 300 MPH. Should cost over $700 a tank, but it's worth it!

 

Hello shadow z.....just got a question....do u own a camaro?.....Cz with all the environment talk it seems like ur car should be a hybrid? And wouldn't the resistants to burn of a higher octane let u run more timing thus increasing power? I personally think it has to do something better or else they would not sell it

 

More timing does not = more power.

Lots of myths being spread around in this thread. I havent noted any spark knock in any condition running on 87 octane with 4 different stock TPI's so I dont really see the suggestion in the owners manual being worth anything.

 

Please learn proper English before you play your BS with me.. No.. I don't own a Camaro.. All of the pictures on my Car Domain are computer generated.. If I was going to lie about owning a Camaro, would I say I owned an '86 IROC-Z? No.. I'd say I owned a 1967 RS/SS with only 5,000 original miles.

What's wrong with enviroment talk? Do you just want to destroy the Earth? There's a HUGE line between responsibily operating/enjoying any V8 car that pollutes more than the typical Honda Civic VTAK, and polluting just because you want to pollute.

What, are you implying that everyone who drives a V8 should be an irresponsible hick with no emissions equipment whatsoever, and emit as much hydrogen as physically possible? If you think that way, grow up. I will most likely, my whole entire life, never own anything that's under 3.0 liters. I'll probably stick to any V8 that's 4.0 liters and up, but you can do that responsibily with proper tuning, and the addition of a couple decently functioning catalytic converters.

You live on this Earth too, do you want to destroy it for future generations? Quit being so self centered. You're not being TOTALLY RADICAL HARDCORE DUDE by saying "enviroment talk". I find it cool to respect the enviroment.

 

I imagine this reply was to crise87, whatever his name is. I mentioned killing power with higher octane gasoline, unless you're running enough timing to fully burn that extra hydrogen/carbon content. That is very true, incase you were doubting it. Higher octane + more timing may not always equal more power, but I do know that higher octane on stock timing will kill power with most vehicles designed to run on 87.

----------------------------

ccrise87 - I've got a few good examples for you here, of why I bring up my crazy non-sense hippy talk, about it being cool to respect the enviroment. You must live in some inner city garbage dump, but I do not. I live 11 miles from a private beach, and try to go there as often as I can, just because I enjoy nature.

It might not look like this a few decades down the road, if everyone continues to carelessly pollute, even by the seemingly small amount of added hydrogen in higher octane gasoline. Take a hint.

- Taken a few weeks ago around the beginning of June, between 4:50 A.M. and 5:30 A.M.

 

do you have any idea WTF your talking about, number one octane is only a measurement in detonation resistance, second of all you say that running 93 on a stock motor is bad for the environment, all gasolines are required to have detergents to prevent sticky carbons, you wont scum up your motor with 93 octane fuel or pollute the environment any more. thirdly you are right about not HAVING to run 93, but dude when the service manuals were written 87 octane fuel wasnt complete **** diluted with ethanol. so yeah i'd say running 87 will isn't good and anybody who knows anything will tell you 87 is only fit for a lawnmower an for 20 cents more why not run premium? and PS 87 will fluffy carbonize your motor way more than 93, because 93 burns hotter and cleaner, and that is a fact.

 

Okay guys, cool down. If your gonna attack eachother, do it in your
emails, not on Thirdgen.org's website which include thirdgen's PM feature. Please dont make this thread a hostile enviroment. We are here for advice, knowledge, and information, not for fighting. If you guys cant get along, then please do not reply towards each others posts.

 

i wasn't trying to argue, shadow z is right on the fact that to high an octane will decrease power an MPGS, but it wont pollute the environment as much as hes stating and as i previously said 87 octane nowa days is junk. if anything put mid-grade in you tune port

 

Gotcha. I felt that this thread was headed south so I had to jump in the middle when I saw coded slang. So lets keep this thread clean. Thanks for understanding comrades.

 

How do you figure that? You should visit where they refine and store fuels sometime. There is nothing worse in 87 octane fuel, it just has a lower octane rating.