What grade Octane should we use

[King Asoka]

I saw Duesergirl's post about what grade gasoline she should use in her 2.4. I thought it might be a good idea to discuss what everyone uses in there tank and why. Give your view of the pros and cons.

Im burning 92 octane in my 3.4L. (In Canada Chevron sells gas with 87,89,92,94 octane levels) I find i get better mileage at the higher octane level. I havent tried the highest octane gas yet, and i dont think i will bother unless i get some serious engine mods done. I also think it burns a little cleaner the higher you go, but that, im sure is debatable. I also find i get less engine knock. Im definatly no expert when it comes to this stuff. So I cant wait to hear what you guys have to say.

[Illarin]

I use regular gasoline.. can't recall what octane level it is. I don't think I'll be upgrading anytime soon either, since gas prices here are topping 2$/gal for regular. >:\

[Grouch]

To keep this conversation in one place I'm moving their post over here. ;)
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duesergirl:
Ok, before anyone asks, I did a search and it didn't come up with anything very helpful. Nick touched on this in that silly thread about the kid with the stock 2.2 running 14 secs, but that was about it and didn't really answer my question.

So, my question is, what difference does it make what octane you put in the car? The reason I ask: I've been hearing lately that you should put in whatever it says in the manual, and not anything higher. Jimmy has always heard that it's good for the car to put in the higher stuff once in awhile, that it sort of cleans the engine out or something. He also says you're supposed to put in one of those bottles of cleaner in once in awhile too, and I said that's not necessary because most gas has engine cleaners in it now, but that's a different story. If it's bad for the car, though, I'd like to know for sure because I want to give him a definate answer before he kills our only means of personal transportation!

Oh, I put this here because that's what type of engine I have, and it is sort of an engine question, I guess. But if this is the wrong place, moderators, please feel free to move this thread wherever it should go!
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wy3134:
You are absolutely correct there in the sense that the manual is correct about the gas...unleaded will be perfect for the 2.2 and its perfectly fine to run premium maybe once a month during the winter and maybe a couple times during the summer, I buy the fuel cleaners at Autozone that match the mileage on my car, usually spending the $8 for the bottle that cleans most of the fuel system, rather than 3 diff. bottles that clean only specific parts of the fuel system. Hope this helps.....

[overdrive75]

It doesn't matter if you go higher than the recommendation in the owners manual, you just aren't supposed to go lower. The higher the octane rating, the longer and cleaner the burn of the fuel.

Case in point, in my Bronco I if I burn 87 I get around 13 mpg on the highway, with 93 I get almost 16 mpg highway. I don't quite understand it. The manual for that say use 87, but with a gain of 3 mpg it's worth running the higher stuff. Also I have been doing this going on 4 years now, with no adverse effects whatso ever. I was even able to advance the ignition timing without having spark knock, and felt a difference in power.

[Redog]

It depends on what mods you have done to your car. I find that if your running an intake (CAI or WAI) you might want to go to 89 (mid grade) but you can stay at 87 (reg) if you want. If you have a S/C or a turbo, you should run at least 91.

After I had my manifold done, on 87 I was getting 6 miles a gallon. I usually put 89 in all my cars but since the price of gas was going up, even last summer, I started to go with 87. With my WAI I was getting a little less MPG, like 23 city instead of 25, but after the mainfold was done, it went to 6 MPG city. Plus it take the PCM about 50 to 100 miles to adjust to any mod, but the lower octanes were just burning up too fast with the mainfold done. I can get about 32 to 35 MPG highway now but I did get 37 almost 38 once.

If you car isn't set up to burn more gas, then reg is fine. The higher octanes will leave too much carbon inside your engine, if used all the time

[johny_boy32]

i use 92 octane in mine and my mpg is really good.....I get somewhere between 24-26 in the city and about 33 on the interstate.

[99ALERO]

use what is recommenced. 87. I believe car and driver had and artical on this a while back. unless you have mods that require it your just throwing money out the window. and stay away from that blend made from corn. i heard horror stories about it eating gaskets and what not.

[ptrudel]

i just run regular...it's cheaper and no difference in performance(without mods)...i'll run super about once a month just for a little cleaning...and as for corn blended fuel, 99alero, ur absolutely right, stay away from that...many many horror stories around here about it...

[jamcllw]

I use the cheap stuff and I get on average about 34 mpg on interstate driving and about 25mpg in the city.

[johny_boy32]

like my auto teacher once said...its the same poop, just a different dog.

[misslindseysue]

Good luck finding gas without ethanol for much longer. I try to stay away from it, knowing I don't have the harder seals, but it's hard to. It becomes more of a problem the longer it sits in your tank, so I don't worry too much, since I have to fill up at least once a week. Most newer cars have the harder seals, etc, that can handle ethanol no problem.

As for octane, I run 87 almost exclusively. I'll put in 89 or 91 when I'm towing, depending on how much 87 is in the tank when I start. I do get better mileage on higher, but I can't make myself pay the extra $0.10-$0.20/gal more.

[Oldsman]

Well here in Chicago area, due to emissions, all we have is ethonal gas.

I notice with that gas running 87 octane i get 24 in town and 31 on highway. with non ethonal 87 i have gotten 26 in town and 33 on highway. I use to normally run 87, sometimes 93. But since i got my MSD on, i am running 89-93. But with gas prices for 93 being $2.15-$2.25 a gal i think i am going to see how 87 does. 87 is just under $2.00/gal.

[ptrudel]

damn i feel dumb askin this, but how much does $2/gal come to in litres?

here gas is .839/litre...

[bdyman]

like my auto teacher once said...its the same poop, just a different dog
^^^^ he`s right
i personally use 93 once a month, the only diff i see is my gas guage goin donw faster and milage is crap
all said is true 93 octane wil not hurt your car at all , i have seen some guys use 114 octane or a racing fuel, and completely burn the cat burn out the upper manifold
89 octane is good for our and most cars out there

[Redog]

Originally posted by 2000_olds_alero@Apr 28 2004, 11:00 AM
damn i feel dumb askin this, but how much does $2/gal come to in litres?

here gas is .839/litre...
There are 3.78 Liters in a gallon

[ptrudel]

:o holly poop...so in other words, ur payin approx $0.529/litre(.74/litre cnd)...i wish gas went down that low here...last time it went down that much was like 3 years ago <_<

[3.4Alero]

I always use 87. It's runnin at $1.759 per gallon in Western PA.

[Pacho]

87 for me too, gas in the Carolinas is running $1.60 for 87.

[BLK03GXS]

Last i bought gas i paid 88.9 cents a L.... b4 it was 77.9 :pissed: lol

But it has been said b4, even with "mods" exhaust and intake etc.. or even msn ignition... our engines are made to run regular gas, the only reason that premium gas exisits is for things like High compression engines, forced induction, and things like BMW's and Ferriaris... (the eco gets close to that at 10:1 compresion but still runs fine on reg BECAUSE THATS WHAT ITS DESIGNED TO RUN ON)
lol
As for runin the intermedate grades... they are all just designed to Suck the consumer in... i doubt you will find a car that calls for medium octane gas... either it runs on reg or premium... thats how it is
So unless you have serious mods, raised compression shaved head or forced induction.. its really a waste of time IMO..... but then we're payin a lot more for gas here... reg was 88.9 a L premium was 99.9 :rolleyes:

[99ALERO]

up here in green bay wisconsin its $1.86 for 87. But your state tax on gas is i believe almost $0.30/gallon!!!!

[2ndAlero]

Ok... first off, this is in line with what I used to do. I worked, for a short time, at designing distillation towers for the seperation of crude oil into gasoline (petrol) and other products.

In summary, use what's in the manual. If it says use 87, then use it. The octane rating has NOTHING to do with the ability of cleaning out the engine or any parts it flows through, burns in, or exits as a gas.

You can stop there if you just want an answer... or continue if you want to learn a bit (more than you'd like most likely) about gasoline and octane ratings.

The octane rating is simply the amount of isooctane (C8H18 for those organic chemists like me out there) when compared to n-heptane. A fuel which is 87% isooctane and 13% n-heptane carries an octane rating of 87.

The octane rating in gasoline is a measure of the gasoline mixture which provides the same "anti-knock" (or knock resistance) as that mixture I mentioned above. So a gasoline with an octane rating of 87 has the same knock resitance as an 87% isooctane / 13% n-heptane mixture. Therefore a gasoline with octane rating of 91 would react similar to a mixture of 91% isooctane and 9% n-heptane. Yes.. before you ask you can get octane ratings above 100. I won't go into that here, but simply understand that you can "create" gasoline which is more than 100% effective when compared to pure isooctane.

So... for reference, where did the 87 come from? Well... Romania to be exact. Oil extracted from Romania (which is/was "light crude oil") when distilled exhibited similar to an, you guessed it, 87/13 mixture of isooctane/n-heptane. It ended up becoming the defacto standard, and has stuck ever since. Since this oil was relatively easy to extract and abundant, this because the mixture that engines were designed around.

So.. you understand the octane rating, but maybe not the "anti-knocking" sense. Knocking in an engine occurs when fuel in the cylinder is ignited by the firing of the spark plug but burns too quickly. If the fuel is burned completely before the ideal moment during the compression phase of the four-stroke cycle you here a "knock". When fuel "burns", remember that it actually explodes. The resulting shockwave from that mini explosion collides with the rising piston, creating a characteristic metallic "pinging" sound.

In a normal running engine (no knocking) the fuel is ignited slightly before the point of maximum compression (piston to top of cylinder) to allow a small time for the flame of the burning fuel to expand throughout the mixture. When this flame arrives too early, for whatever reason, that is when the knocking effect occurs. If you run your engine with it knocking you can cause vibration and damage to the engine.

So... what happens when an engine "knocks"? That means you are burning the fuel "too soon". The fuel is ignited by the spark of the spark plug and also from the compression in the chamber (anyone have physical chemistry?? you would have covered this for sure in there. If you talked about the Ideal Gas Law in general chemistry you should understand the decrease in pressure of the chamber and what is going on inside the engine). Anyway... if the engine is knocking, you need a fuel which will ignite later. How do you get that?? A higher octane rating. The higher the octane rating the harder it is to ignite.. but yet it gives you more energy. The isooctane contains the energy you are using... so a higher octane means more energy in the fuel. More engery is hard to get to, and why it is hard to "burn" in the engine.

What's happening in your engine if you are running a higher octane than you should?? Well.. depends on how much higher and for what length of time. Remember that a higher octane needs more compression (unless you change the spark energy) to "ignite". That generally means you are igniting the fuel when the piston is closer to "dead top". Can you damage your engine running 89 in something designed around 87. No... most likely you are simply blowing by un-ignited fuel and using your cat. converter to hopefully burn it out. If you continue to run higher octane that required and run for long periods of time or under load (i.e. = engine and exhaust are really hot) you could hear backfires of the unspent gas being ignited in your cat/exhaust system.

In the end.. running an 89 or even 91 octane rating gas in your car designed around 87 isn't going to hurt you. You're spending money that you are most likely not gaining benifit from though.

Sorry for the long post... but something I know a thing or two about and I always like it when I can educate people a bit. Hope others found this helpful.

If you would really like to learn more about gasoline, there is a FAQ out there that provides a great deal of information. It can be found at:

http://www.faqs.org/faqs/autos/gasoline-faq/part1/

[misslindseysue]

Man, I miss school. And chemical engineering. *sigh*

[King Asoka]

thanx 2ndalero for that very educational dissertaion on Octane. That was more than what i was looking for, and i thank you for sharing your knowledge with us.

i think its time to go back to a lower octane.... :mellow: and start saving a few bucks.

[smokinAMD]

87 all the time, I'm too cheap to use the other stuff.

[ptrudel]

:huh: :blink: thats' a hell of an explanation..

[2ndAlero]

Originally posted by 2000_olds_alero@May 2 2004, 08:05 AM
:huh: :blink: thats' a hell of an explanation..
Well... that's what you get from a Chemical Engineer who used to design oil refinery plants. :D

I said it was going to be long, and gave a quick summary. Hope it's usefull.

I might not have the most posts (like Silent), but mine might be the longest on topic posts of anyone here!

[BLK03GXS]

Theres a Guy who KNOWS how to use the ENTER key... Finaly lol
Nice explination :thumbsup:

[StealthAlero]

thankyou 2ndAlero, you saved me a long write-up.

[gxryan]

My friends old 89 S10 wouldent idle at all with 87 octane but once we put in 91 it would purr like a kitten. I also noticed this with my 90 Lumina with a 3.1L V6 the EGR was just bunnyed and whenever i would let the car idle down from highway speed i'd get a service engine lite. But if I ran 91 octane in there the lite would never come on. But i found after running that 91 octane for about 4 months that all the power it gave me at first was gone so I went back to 87 and never got that service engine lite. So that 91 definately helps clean up carbon filled older engines.

And ya that ethanol gas sucks it chewed up 02 sensors in my Lumina. But I can't beat the price of it here for 91 octane. ( I can get ethanol gas with 91 octane for the same price as 87 octane regular gas) I dunno if thats the same as all over the world. but it's really tempting

[1WhiteOSV]

I use premium in my 3400 alero....i've had it for a year and NEVER had problems relating to the premium gas....RIGHT NOW the premium is 2.19/gallon :pissed: so i have switched to mid-grade for the time being...but any1 who says that premium is "unsafe" is just WRONG. 6pts more octane will NOT hurt ur car..it helps it run more efficiently

[2ndAlero]

Originally posted by 1WhiteOSV@May 13 2004, 10:43 AM
I use premium in my 3400 alero....i've had it for a year and NEVER had problems relating to the premium gas....RIGHT NOW the premium is 2.19/gallon :pissed: so i have switched to mid-grade for the time being...but any1 who says that premium is "unsafe" is just WRONG. 6pts more octane will NOT hurt ur car..it helps it run more efficiently
I'm not going to bother arguing with the misinformed, uneducated masses...

Spend your money however you'd like... there is no need to go beyond the 87 octane though.

[BLK03GXS]

Originally posted by 2ndAlero+May 13 2004, 11:56 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (2ndAlero @ May 13 2004, 11:56 PM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-1WhiteOSV@May 13 2004, 10:43 AM
I use premium in my 3400 alero....i've had it for a year and NEVER had problems relating to the premium gas....RIGHT NOW the premium is 2.19/gallon :pissed: so i have switched to mid-grade for the time being...but any1 who says that premium is "unsafe" is just WRONG. 6pts more octane will NOT hurt ur car..it helps it run more efficiently
I'm not going to bother arguing with the misinformed, uneducated masses...

Spend your money however you'd like... there is no need to go beyond the 87 octane though. [/b][/quote]
Thankyou... some one who has common sense...
This thread is gunna get as dumb as the one in "off topic" that died a few weeks ago, where me and redog went at it... :rolleyes:


http://invision.aleromod.com/index.php?showtopic=3671

[dopey]

i used 110 octane. i prefer cam2 though........ or just straight avation fuel, my car really flys when i use that stuff!!!!!

[BLK03GXS]

Originally posted by SweetAlero99@May 14 2004, 02:33 AM
i used 110 octane. i prefer cam2 though........ or just straight avation fuel, my car really flys when i use that stuff!!!!!
LOL i bet....

OR better yet? just get some SOLID FUEL ROCKET BOOSTERS lol...
that should save on buildups and deposits ... :P :D

[dopey]

^^^ only at the track...

[BLK03GXS]

Your right Sweet... it would be dangerous to use power like that on the street....
like a heat sheild mod :D :P

[1WhiteOSV]

ALL I said was that using premium gas will NOT hurt someone's car! Thats it!....I am not "misinformed" or "uneducated". It's not like I said I used Octane Booster or F*ing racing fuel! Jesus..you guys take things WAAYY too far.

[dopey]

^^^ ur just really annoying

[mfuller]

I use 93 because the increased timing of my DHP requires it. But with fuel prices spinning out of control, I may re-install the stock PCM and start burning the cheap stuff again.

[Oldsman]

if you run cam2 or similar................better have extra O2 sensors

[dopey]

^^^ i doubt many know what cam2 is. god i love the smell of that stuff. nothing like a 455 passing u by burning cam2

[3.4 Euro Alero]

If anyone still cares, it is a proven fact by 3 different dealerships here in the Ottawa area that the majority of newer 3400 engines actually prefer and runs smoother on 87 octane. I am one of those guys who liked to run HighTest all the time, but found my first 3.4 was a little rough and sometimes difficult starting. GM tech's and foremen have no idea why, but it just doesn't like 93 for some odd reason. Both of mine have run better on 87, but car to car, each is different.

[theirishgonzo]

wht you need to do is add 20 % nitro to your fule lol

here in mich most of the gas stashon sell the stuff with ethonal in it.

[AlbinoMonkeyRat]

I use 89 when I know I'm going on the thruway, because I do get better mileage that way. But when I know I'm NOT going to use the thruway, I'll use 87, just because it's cheaper.

Back in December when I drove out to CT (about 400 miles away) I only stopped once and had about 3/4 of a tank left when I arrived. So figure, that's about 300 miles per tank. Not bad on a stock 2.4 doing well over 80 mph the whole way. But on 87, I get about 200-250 miles per tank. Must be all that idle burning. :unsure:

[jbilyeu]

I use mid-grade (89 octane) unleaded. Around here it is the same price or cheaper that regular, because in the midwest they push ethanol (the corn blend). As far as people saying ethanol is bad for cars, well you were right. I can't remember where (I want to say Car and Driver, but I might be wrong), did a huge article about it. When they first started making ethanol blended gasoline, it caused vapor lock and had an adverse effect on the quality of your intakes and such. They refined their processes now where ethanol burns cleanly and effeciently without causing damage to your engine.

Jon

P.S. That Shell V-Power crap that they sell as their premium grade now, sucks.