Celica Forums General Discussion Engine and Performance octane/gas question

does it matter wat kinda octane i put in my car? does it really perform better on higher octane? wats the best to use for my GT?

whats best is what the book tells you, if it dont need premium dont put premium. a lot of ppl think that higher octane always means better performance but thats wrong, putting high octane gas in engines that are designed for lower octane will screw up your engine!

^^^^

it will not hurt your engine to put a higher octane in it. and i feel that my car accellerates best with 92 octane. i used 89 but it didn't feel as good.

I put 98 octane for my GTS seems fine though

^you're suppose to use at least 91 for GTS. as for a GT, 89 would be more than enough...

The celica manual says 91 for gt...

don't own a GT, scan it for me...

Hold on

Hm... guess you were right.

1ZZ-FE engine
Unleaded gasoline, Octane Rating 87 (Research Octane Number 91)

2ZZ-GE engine
Select premium unleaded gasoline with an Octane Rating of 91 (Research Octane Number 96) or higher for optimum engine performance.

GT's 1ZZ-FE right?
anyways what the hell is research octane number?

GT is 1zz-fe...

I think higher octane should make your car perform better. That why their is racing fuel such as CAM2 that high on octane.

so it says 87 for GT. so does that mean anything higher woundn't help? or are they saying that it's ok...

It doesn't say like the GTS like 91 or higher

Columbia Encyclopedia definition of octane number:

figure of merit representing the resistance of gasoline to premature detonation when exposed to heat and pressure in the combustion chamber of an internal-combustion engine. Such detonation is wasteful of the energy in the fuel and potentially damaging to the engine; premature detonation is indicated by knocking or pinging noises that occur as the engine operates. If an engine running on a particular gasoline makes such noises, they can be lessened or eliminated by using a gasoline with a higher octane number. The octane number of a sample of fuel is determined by burning the gasoline in an engine under controlled conditions, e.g., of spark timing, compression, engine speed, and load, until a standard level of knock occurs. The engine is next operated on a fuel blended from a form of isooctane that is very resistant to knocking and a form of heptane that knocks very easily. When a blend is found that duplicates the knocking intensity of the sample under test, the percentage of isooctane by volume in the blended sample is taken as the octane number of the fuel. Octane numbers higher than 100 are found by measuring the amount of tetraethyl lead that must be added to pure isooctane to duplicate the knocking of a sample fuel. At present three systems of octane rating are used in the United States. Two of these, the research octane and motor octane numbers, are determined by burning the gasoline in an engine under different, but specified, conditions. Usually the motor octane number is lower than the research octane. The third octane rating, which federal regulations require on commercial gasoline pumps, is an average of research octane and motor octane. Under this system a regular grade gasoline has an octane number of about 87 and a premium grade of about 93. Most American-made cars that were built in the 1971 model year or later can use regular gasoline. To prevent knocking, premium grade gasoline must be used in many cars built before 1971 and in some new cars that have high-performance engines.

There you have it

Nice~ thanks for the info
so the pumps in the us are average of those two.
Still most of the pumps tell you right under the big numbers
I'll haveto look for that next time

the higher the better always and also better for the engine i used 91 up for my cavalier and i felt it ran better on that

i have to use 91 up the gts i would anyway even if i had a gt

http://www.handymanusa.com/articles/octane.html

This and every other article I've read indicate that there is no benefit to using higher octane than what the engine is designed for. The reason suped-up sports cars use higher octane gasoline is because they have higher compression ratios and need the higher octane to prevent premature detonation, not because the higher octane has any performance benefits itself. If you're not getting premature detonation, there is no reason to go to a higher octane.

really...
That'll actually help my wallet and save more for other parts.
Thanks

I'm aware of all the literature and the mechanics behind it, but why does every GT owner here who puts in 91 (including myself) swear that the car feels slightly better? Even veteran members on this site very knowledgable about cars put 94 in the GTS because they feel a difference too. If you put 91 in a Ford Taurus, a Honda Civic DX, or some other random, general car it won't do much but the Celica GT isn't exactly an average car. My theory is that the 1ZZ's higher-than-average compression helps take advantage of 91.

The first time I floored my Celica it gave me butterflies in my stomach (I suspect the dealer put 91 in the tank, he didn't know what he was doing) and that first tank I had a lot of fun. Every tank after for 6 weeks was 87, and it just didn't feel the same as when I first bought it. On a whim one night I filled up with 91, turned out of the gas station and floored it. Butterflies in my stomach again.

I'm currently testing out 89 on my car and so far haven't noticed a difference compared to 91, and my idling problem has gone away (probably a combination of other factors). I'll be testing this out for a few months, you can see my thread here:

https://celicahobby.com/ubbthreads/thread.f_1953333755_0_collapsed_5__1.html

A GT can safely take 87, the best thing you can do is to try out different grades yourself and find which one you personally think is right. There is always going to be a debate on this...

EDIT: I see a lot of noobs posting here and very few vets with real experience, maybe some of you guys could help us out.

first of all, dont assume that just because it doesnt say "elite member" under our name it means we dont know anything. now whatever you ppl with gt want to do with ur car whatever, but you guys have a comp ratio of 10.00 to 1 while we gts owners have 11.50 to 1.

The octane grades are designed to accommodate engines with different compression ratios. High compression engines, found in most performance cars, require a fuel that burns efficiently at a higher temperature. Thats what premium fuel does, it burns hot under high compression. In a normal engine, premium fuel does not burn completely, resulting in excess carbon build-up and carbon fouling of the spark plugs. The end result is a less efficient engine that requires tune-ups more frequently.

hope that helps

"would you like some pancakes?...bitches" <-- chapelle

for a gt - use 87 or above
for a gts - use 91 or above

i use 93

10:1 is still higher than average. (I doubt many people will agree that the 1ZZ is a "normal" engine.) It's low enough where it can take 87, but you still haven't explained why so many GT owners will swear that 91 is slightly better. Sure it might cause damage in a car that was designed strictly for 87 (again, cars like a Ford Taurus) but from the number of GT owners on this site using 91 I doubt it's causing damage.

I'm sorry if I implied anything about your intelligence level, but if you look through all the posts there are only a handful that have been on this site a long time. if you've read any of the other gas threads you'll see there are a lot of people on this site with lots of knowledge about this, and I was inviting them to toss their $.02 in. I know that some people join this site already with lots of knowledge and that you can't judge them on their post count.

If you guys really think you feel a difference with premium gas in a GT I won't argue... but logically, there is just no way.

Once you are using the octane level at which the engine is no longer knocking, there is no benefit to using higher octane gasoline. If the GT requires 91 octane to avoid knocking, that would mean the GTS would require what... 93... 95? The GTS and GT certainly can't require the same type of gasoline. Since some states don't even SELL above 91 octane at the pump, I find it hard to believe Toyota designed the 2zz engine to require higher than 91... which make me greatly doubt the 1zz can require higher than 89.

GT will not knock at 87
GTS will not knock at 91

I'm not talking about requirements, i'm talking about what works good. 91 is not required for a GT, but it works good.

There is no difference in performance. The higher the octane rating, the more resistant it is to detonation. unless your car is tuned to run premium, stick with regular.

If you run 93 octane in a car designed for regular, not all that fuel is going to be burned in the combustion process. Yes, your car will idle a little smoother, but a lot of that fuel is just gonna burn in your cat or go out the tailpipe. not very smart, especially with gas being so expensive these days.

If the engine has high compression, or the timing is advanced, you may want to raise the octane a bit. if you reprogram your ECU, run a stand-alone or get a chip (a real chip, the kind that actually has a new program rom) then you want to run a higher octane. Otherwise, stick to regular for sure, or it's just money down the drain.

GTS owners are advised to run 91 octane or higher, Best results seem to come from 93 octane, but in the GTS, the manual suggests 91 or higher (meaning, you can go as high as 100 octane, since anything more will be leaded fuel)

Hell, I remember when people were flipping out in the 70's over the gas crisis. Fuel prices got as high as $1.65 a gallon.

These days, fuel costs are even higher, yet people don't seem to care one bit this time around. They buy SUVs and don't seem to have a care in the world...

Just wait until you start seeing gas station lines that reach around the block, and they start rationing fuel; it'll be the 70's all over again, but people are still oblivious.

Honestly, if your car can run regular, run regular in your car. Only put something higher in if they are out of regular at the station. anything more is just wasteful, and believe me, nobody misses it until it's gone.

Butt dyno is pretty inaccurate

^^yea you prob did..i kno i did but being who i am im lazy and i just made another topic.

but anyways thanks for the advise. i think imma just continue putting 89 in my car. it seems to wrok well and its not all the way premium. but feels better to me then 89

oh yea and thanks for all ur $.02 everyone. anyone else who wanna comment are welcome to ur opinions...man i love everything celica..and the ppl here

Yeah I love you too man. And all yall!!!

exactly...

but for me i have to use the premium 93 or else it will knock

Everyone is wrong with every explanation in this thread.
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What are octane ratings?
Octane ratings are a measurement of a fuel's ability to resist detonation.

What is detonation?
Detonation is when the fuel combusts before the spark plug sparks. This happens when a fuel's octane rating is too low for the compression in the cylinder. Detonation is also called knock or ping.

Cranking Compression vs. Octane Requirements [2strokeheads.com]
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Most naturally aspirated cars run a 10:1 compression ratio, where BDC--bottom dead-center--is 1atm of pressure and TDC is 10 atmospheres. 87 is the minimum octane rating for 10atm (147psi) of pressure. As you increase the compression ratio, you increase the peak pressure, and the higher the peak pressure, the higher the octane you need so that the fuel doesn't detonate.

A forced induction engine, e.g. turbocharged or supercharged, needs higher octane than a typical passenger car engine because the cylinders operate at higher peak pressures, even if the engine runs a lower compression ratio, because the pressure at BDC is more than 1atm. The 2zz runs at 11.5:1 compression naturally aspirated, so 1atm at BDC becomes 11.5atm (169psi) at TDC, and 87 octane will detonate before it reaches 169psi. A Subaru WRX STi runs at 8.2:1 compression, so TDC is only 8.2x more than BDC, but BDC isn't 1atm when air is being forced into the cylinder. Assume a 10psi turbo or supercharger boost, that's 14.7psi (1atm) + 10psi = 24.7psi (1.68atm), now compress to TDC and you get 24.7psi x 8.2 = 202.54psi (13.78atm).

If you think your 1zz or other 10:1 engine runs better on 91 or 93 octane, you're dreaming. Octane does nothing to improve torque or power or any other aspect of your engine's operation. Running racing fuel in a stock naturally aspirated, turbocharged, or supercharged engine does nothing for you either, unless you've raised the compression ratio and/or increased the BDC pressure with a big/bigger air compressor, then you'd have to measure your max cylinder pressure to calculate what minimum octane rating you need to prevent knocking.

I ran my 2002 GTS Auto on cheap 87 Octane gas for a couple years, did not hear knocking or rough idling.

The engine runs smooth and strong now with 91 Octane. I may try it on a couple 87 tanks again to see how it does.

My 2002 GTS has 330K miles. User manual says use min 91 Octane.

Couple years ago when gas price was high I ran it a few years on 87 Octane, long trip high speed cruises every week. Never had a problem.

Now gas price is high again. I test drove a couple tanks of 87 Octane, city stop and go, long high speed cruises. The most severe test was to climb a steep hill on 4th gear. The engine was weak and way overdriven but did not knock. So 87 Octane is OK with the GTS' 2ZZ engine in most driving unless you want maximum power for racing..

Old 2ZZ engine may knock due to carbon deposits' preignition. Use GUMP OUT or GUNK to clean out valves, pistons ,cylinders and flush out deposits. Engine will run a lot smoother, stronger and leaner.

At sea level, the GT-S won't achieve max ambient pressure at BDC unless the throttle is wide open and the RPM is high enough to switch to the second cam profile. The second cam profile allows the valves to open a little more, thereby letting the engine breath a little easier. The second profile kicks in at 6,000 RPM. So 87 and 89 octane are probably fine for normal driving at any altitude, but below 10,000ft, you need 91+ octane when the RPM gets to 6,000 at full throttle.

If you use 87 or 89 in your GT-S, do not rev the engine to 6,000+ RPM.

This is why manufacturers specify minimum octane requirements, it doesn't need it most of the time but there's so many nuances to the physics, it's easier to just say "91 octane or higher" and never risk knocking the engine than to explain all the different scenarios where a lower octane is acceptable.

Gas prices have gone up higher than I ever known due to the war in Ukraine. Cheapest gas is Arco, Regular $5.79 Premium $5.89.

Premium is only 10 cents or 1.7 % more a gallon.

I will use Premium.