View Full Version : What type of octane I should use???
krakkhenz
02-14-2006, 11:18 AM
Im a little confused about this, my car seller told me that I should use 95 octane gas, but the manual says I should use 91 :confused:
What are the difference between 91 and 95???
My yaris got a 1.3 engine.
I'd go with what the manual says.
The difference between octanes is how much pressure is required to ignite the fuel. The higher the rating the harder it is to ignite the fuel.
I thought the car (Yaris) can run on 87?
I thought the car (Yaris) can run on 87?
The rest of the world measures octane differently then we do in North America.
oh, didn't saw the OP was from Panama... :tongue:
as400g33k
02-15-2006, 09:15 PM
the yaris is rated to run at 91 but can also accept higher octane. most people would claim a performance boost when using higher octane. while some would even claim better fuel efficiency with higher octane.
we use 91, as it is cheaper than 95, 98 or 100 octane. :)
the yaris is rated to run at 91 but can also accept higher octane. most people would claim a performance boost when using higher octane. while some would even claim better fuel efficiency with higher octane.
we use 91, as it is cheaper than 95, 98 or 100 octane. :)
100 octane!! It's gonna burn like :evil:
Don't worry friend, the higher is the octane no., the harder it is for the fuel to burn:smile:.
Hi guys! So the harder for the fuel to burn is not good in the long run? I have a TS model, I currently use 95 octane... What if I were to use 98 or 100 octane fuel, what would change? Would the car run better or would I feel a bit more power or torque, or is all this just BS?
Use what is recommanded in your user manual...
http://autorepair.about.com/od/enginefuelgasolines/a/highoctanegas.htm
Hi guys! So the harder for the fuel to burn is not good in the long run? I have a TS model, I currently use 95 octane... What if I were to use 98 or 100 octane fuel, what would change? Would the car run better or would I feel a bit more power or torque, or is all this just BS?
Unless you are experiencing rough running or misfires, then odds are the car would not run smoother.
However there prolly would be a slight increase in tourque and fuel mileage with higher octane fuel.
With fuel that is harder to burn, the spark timing can be set better, and the detonation can be more exact. This also means that the computer can use a more exact air/fuel ratio.
The thing is if your vehicle is stock, it might not make a difference that you could actually feel in everyday driving. The only way you could tell is by using a dyno, and that gets really expensive.
krakkhenz
02-16-2006, 12:27 PM
ummm... thanx for your replies, im using 95 octanes since the first day, but im gonna try with 91 and set the trip B for the next refuel.
Use what is recommanded in your user manual...
http://autorepair.about.com/od/enginefuelgasolines/a/highoctanegas.htm
Actually, you and why? know a lot:smile:!
Thanks guys! I have no problems at all with the car, it runs great! I just didn't know the low down on the higher octane stuff... I guess I'll just stick with Shell 95 octane fuel. Oh yeah, Shell has a V-POWER 95 octane fuel as well besides the V-POWER RACING 100 octane fuel, do any of you have opinions or experiences on the V-POWER 95 octane fuel? Supposedly it contains some additives or something extra that the regular 95 doesn't...
No experience with it, I don't remember seeing anything like that marketed over here.
But additives usually do something interesting, so you could give it a try and see what it does, but since it is the same octane, it prolly will only do things like clean the engine, I don't think it would make a difference in the power output of the vehicle.
No experience with it, I don't remember seeing anything like that marketed over here.
But additives usually do something interesting, so you could give it a try and see what it does, but since it is the same octane, it prolly will only do things like clean the engine, I don't think it would make a difference in the power output of the vehicle.
Yeah, this is also what I heard, that additives really do something to the engine which is not really harmful, but rather good for the engine since it cleans it somehow! :thumbup: I might give it a try though... :thumbsup:
yariman
02-18-2006, 07:13 PM
Additives help clean the fuel system etc. but you are only wasting money using higher octane thinking that the Yaris will benefit from it. As I mentioned in another post, unless you change your prom fuel/timing maps you can't advance your timing or add more fuel to even get detonation.
Additives help clean the fuel system etc. but you are only wasting money using higher octane thinking that the Yaris will benefit from it. As I mentioned in another post, unless you change your prom fuel/timing maps you can't advance your timing or add more fuel to even get detonation.
I got ya Yariman, thanks for the input! :w00t:
ECU's from the factory can adjust. They have to adjust in case you get a bad tank of fuel, and they can adjust a little the other way as well.
AutoTech1
02-24-2006, 02:23 PM
There is no need to run higher octane fuel than what is stated in your manual. You'd just be wasting your money. Higher octane fuel is mostly used when some form of forced induction is introduced. This higher octane helps to prevent detonation, which can destroy a motor. Why do you think many European cars require higher octane fuels? Because they come with turbo's and superchargers from the factories...:wink:
AutoTech1
02-24-2006, 02:27 PM
Hi guys! So the harder for the fuel to burn is not good in the long run? I have a TS model, I currently use 95 octane... What if I were to use 98 or 100 octane fuel, what would change? Would the car run better or would I feel a bit more power or torque, or is all this just BS?
You don't need higher octane, unless you are running some set up that requires it. You are wasting your money on protection you don't need.
ECU's from the factory can adjust. They have to adjust in case you get a bad tank of fuel, and they can adjust a little the other way as well.
Can you tell me more about ECU's adjusting and adapting to higher or lower octane fuel? They do it automatically? What happens if you switch from 95 octane to 98-99 octane, what does the ECU do to make it good for the car, does it run better or what? :iono:
You don't need higher octane, unless you are running some set up that requires it. You are wasting your money on protection you don't need.
I was just curious cause many people have this issue, whether the car runs better or not, or is it better at all for the engine and such?
An Ecu will prolly not adjust for all octanes. I do believe it will adjust some for higher octane fuels, just as it adjusts if you get a bad tank of gas. How much it adjusts and wether or not it is actually worth it depend on the cost of fuel and are questions that cannot be answered without extensive testing.
As to what it would do, it would advance timing and lean out the fuel ratio so that a more precise explosion will happen every time, this would make the car more powerful and get better gas mileage.
There only way to find out if it benefits you is to try it and keep records of power and gas mileage you get with each octane level.
An Ecu will prolly not adjust for all octanes. I do believe it will adjust some for higher octane fuels, just as it adjusts if you get a bad tank of gas. How much it adjusts and wether or not it is actually worth it depend on the cost of fuel and are questions that cannot be answered without extensive testing.
As to what it would do, it would advance timing and lean out the fuel ratio so that a more precise explosion will happen every time, this would make the car more powerful and get better gas mileage.
There only way to find out if it benefits you is to try it and keep records of power and gas mileage you get with each octane level.
Yeah I agree, extensive testing is necessary! How about what AutoTech1 said,
"This higher octane helps to prevent detonation, which can destroy a motor."
I don't quite understand this???
Detonation is also reffered to as knock, pinging, etc.
What it means is the fuel is igniting before the engine is ready for it to explode. If it happens in a big enough quantity it can cause the pistons to be pushed clear out the other side of the engine.
This is why modern cars are created to adjust for a bad tank of fuel.
The reason to use the octane the manufacturer recommends is because the engine is designed to run on that octane with no detonation. Switching to a lower detonation could cause detonation. Switching to a higher octane should not effect detonation, as there should be none on a stock car using the manufacturers recomended octane fuel.
However on modified cars, especially forced induction vehicles, they use the highest octane they can get their hands on because it helps to prevent detonation, not to mention it means they do not have to tune the vehicle quite as much.
The biggest reason for modified vehicles having detonation is laziness of the tuners.
yariman
02-25-2006, 11:19 PM
Hey ToTo, Simply, todays engines are designed within certain parameters to run best on a certain fuel for best performance and low emissions. The engines computor receives signals from various sensors such as how much air is being drawn in and at what temperature. timing, crankshaft position, engine speed sensors, vehicle speed sensor, EGR sensor, air-conditioning sensor, knock sensor which senses if the engine is knocking so the computor can retard timing. Oxygen sensor and on and on. The computor takes all the inputs from these sensors and adjusts whatever is needed to run at "stoichiometric" air-fuel ratio which is the air-fuel ratio which produces the most complete combustion with the fewest harmful byproducts. This gives the best compromise of power, economy and emission control. Now once again if you want to get better performance , you have to change those computor parameters. However, low emission output will be lost.
AutoTech1
02-26-2006, 05:57 PM
I was just curious cause many people have this issue, whether the car runs better or not, or is it better at all for the engine and such?
The car has no performance gains and it doesn't do anything more than what your recommended octane does.:wink: Octane is choosen to resist detonation. Here is a link that explains more of what I was trying get at as well as why?: http://www.geocities.com/runyardj/OctaneExplanation.htm
AutoTech1
02-26-2006, 06:11 PM
Detonation is also reffered to as knock, pinging, etc.
What it means is the fuel is igniting before the engine is ready for it to explode. If it happens in a big enough quantity it can cause the pistons to be pushed clear out the other side of the engine.
This is why modern cars are created to adjust for a bad tank of fuel.
The reason to use the octane the manufacturer recommends is because the engine is designed to run on that octane with no detonation. Switching to a lower detonation could cause detonation. Switching to a higher octane should not effect detonation, as there should be none on a stock car using the manufacturers recomended octane fuel.
However on modified cars, especially forced induction vehicles, they use the highest octane they can get their hands on because it helps to prevent detonation, not to mention it means they do not have to tune the vehicle quite as much.
The biggest reason for modified vehicles having detonation is laziness of the tuners.
That's also a great point... Most people think that adding a turbo is easy. You just go to a shop and they install it for you... That's it right? WRONG... You have to think about many things... For example: If I do this modification, how will it affect my car overall? What are the risks? What is necessary and what is optional? This goes back to modified vehicles having detonation because of lazy tuners like why? was getting at... Every step in modifying a car usually leads to another step... It's not as easy as shown in the movies, but when it's done right (And through the pain of working long hours and getting little sleep; unless you are born rich) it can sure be rewarding.:wink:
Thanks guys for the inputs on the higher octane business... I will just rather stick with the recommended octane, cause I don't want to just simply waste money for nothing. At the beginning, I did think that it might help or do something to clean the engine or add a little bhp, but oh well...
The car has no performance gains and it doesn't do anything more than what your recommended octane does.:wink: Octane is choosen to resist detonation. Here is a link that explains more of what I was trying get at as well as why?: http://www.geocities.com/runyardj/OctaneExplanation.htm
I disagree with that statement. I believe using a higher octane might get better gas mileage and a little better performance.
I believe this because all manufacturers use 93 octane in the USA for all the testing.
I disagree with that statement. I believe using a higher octane might get better gas mileage and a little better performance.
I believe this because all manufacturers use 93 octane in the USA for all the testing.
And what about adding acetone to fuel? What does this do, which I found on the Toyota Owners Club (http://toyotaownersclub.com/forums/index.php?showtopic=44575) home page, plus also some links in the forum topic as well of this subject... :confused:
Acetone used in very small amounts adds gas mileage. Acetone used in too big amounts destroys hoses and anything else in an engine that is not metal.
Note that is around .78 cc per liter or one ounce per 10 gallons. Not more than three oz. per 10 gallons.
http://pesn.com/2005/03/17/6900069_Acetone/
"Incidentally, in almost all cases, the lowest octane is best for mileage. Most modern vehicles do not have high enough compression to justify using high octane fuels. The testing indicates best mileage is usually obtained with 85 or 87 octane gasoline. Too much octane causes a loss of power and economy. BUT too little octane causes the same things plus knocking. Listen carefully to your engine for tell-tale knocks or clicks when you start out from a light. The best mileage points to the correct octane when the engine is properly tuned. See your owners manual."
I would check it out with the dealership first to see if adding this kind of additive to the gas will void the warranty:iono: .
yariman
03-02-2006, 02:06 AM
You would be wise to stay away from acetone. C'mon gang we are not mixing fuels for funny cars, stick in what ever octane makes you feel better. If saving some money feels good then pour in 87 octane, it's all you need in Uncle Yaris.
If it works to increase gas mileage then why not use it?
yariman
03-02-2006, 12:21 PM
Once again it is controversial whether it even helps get better milage, but it is known to destroy certain rubbers. So with the already decent mileage that the Yaris gets, why look for trouble?
This dude supposedly doubled his gas mileage in his neon. (http://pesn.com/2005/03/17/6900069_Acetone/) 40 mpg is good, but if you could get 60, or even 80, wouldn't it be worth a try?
Plus, at the tiny levels used to get the suppsed outcomes, acetone will do nothing to any engine internals.
Add to that that acetone costs very little, and I think it is at least worth a try.
jcove
03-02-2006, 08:21 PM
This dude supposedly doubled his gas mileage in his neon. (http://pesn.com/2005/03/17/6900069_Acetone/) 40 mpg is good, but if you could get 60, or even 80, wouldn't it be worth a try?
Plus, at the tiny levels used to get the suppsed outcomes, acetone will do nothing to any engine internals.
Add to that that acetone costs very little, and I think it is at least worth a try.
http://www.pureenergysystems.com/news/2005/03/17/6900069_Acetone/
Here's another link....
Sounds like it would be worth a try.
If any members have tried acetone, please post the results. By making this request, I am not recommending or encouraging anyone to go ahead with trying. I just want to know if anyone has tried it and what's the result. I personally would wait until some gasoline additives manufacturers market products that contain acetone so that if anything goes wrong after I have used their products, I can hold them responsible.
yariman
03-03-2006, 01:52 AM
A while ago during a deisel electronics course we got into fuels and additives etc. That's were I heard that some people thought there were milage gains and some not. Acetone does destroy some plastics and rubbers. Possibly this could take some time being so diluted in gas, if it even ends up happening at all. Be very careful of a warranty issue. If you have an engine warranty issue what do you think the dealers going to say if they happen to find acetone in your fuel? Yes you would challenge them about the fact that the acetone actually caused your problem but what a pain in the ass. Another fact mentioned in my class was that if acetone really improved milage so much how come one of the gas companies isn't adding some to their fuel and stating that their fuel actaully increases milage and cornering all gas sales? Just my opinion from what I have heard.:iono:
AutoTech1
03-03-2006, 12:57 PM
I disagree with that statement. I believe using a higher octane might get better gas mileage and a little better performance.
I believe this because all manufacturers use 93 octane in the USA for all the testing.
If you believe that why don't you just jump into a pile of BS???
AutoTech1
03-03-2006, 12:59 PM
If it works to increase gas mileage then why not use it?
Because it doesn't. It's one of those circulated myths... It does nothing for you, except waste your money, because your car doesn't need it. It's not a Supra or a Lexus or a Beemer or a Porsche. Just get over it.
AutoTech1
03-03-2006, 01:05 PM
I would check it out with the dealership first to see if adding this kind of additive to the gas will void the warranty:iono: .
It won't void the warranty. Sure, you can use a higher octane, but you'll void common sense, if you void anything...:redface:
So you've done tests with it? If so, where is your data? If not, you can't possibly know if it does something or not.
It won't void the warranty. Sure, you can use a higher octane, but you'll void common sense, if you void anything...:redface:
I was talking about whether adding acetone to the gasoline(not about using higher octane gas) could void the car's warranty. Yariman seems to agree that this is a reasonable concern(thanks Yariman). I think it is common sense that putting uncommon additives into the gasoline may void the warranty:smile:.
AutoTech1
03-03-2006, 11:03 PM
So you've done tests with it? If so, where is your data? If not, you can't possibly know if it does something or not.
Sorry. I thought you were asking about octane still.:redface:
As with acetone, it makes perfect sense, but I have never tested it, so I can't say that it does/doesn't work... But how it was explained, it sounded like it'd work.
Adriaan
03-04-2006, 12:25 AM
from experince with previous cars i've only used 91 octane on long distance drives and there you do see a difference, since the long drive cleans out the car the high octane help also. with my paseo normal gas i got abot 400km and with 91 octane 430km. for my corolla 440km normal 465 km 91 octane. I'll see when i make that trip to toronto in the spring.
from experince with previous cars i've only used 91 octane on long distance drives and there you do see a difference, since the long drive cleans out the car the high octane help also. with my paseo normal gas i got abot 400km and with 91 octane 430km. for my corolla 440km normal 465 km 91 octane. I'll see when i make that trip to toronto in the spring.
How about this? New cars benefit little from higher than user's manual specified octane no. but old cars benefit more. In my experience, new cars do not knock/misfire often(knocking will automatically result in low efficiency). Old and badly maintained cars knock more often and so they stand to benefit from higher octane no. fuel:smile:.
Sorry. I thought you were asking about octane still.:redface:
As with acetone, it makes perfect sense, but I have never tested it, so I can't say that it does/doesn't work... But how it was explained, it sounded like it'd work.
lol, ok.:bellyroll:
AutoTech1
03-04-2006, 02:59 PM
from experince with previous cars i've only used 91 octane on long distance drives and there you do see a difference, since the long drive cleans out the car the high octane help also. with my paseo normal gas i got abot 400km and with 91 octane 430km. for my corolla 440km normal 465 km 91 octane. I'll see when i make that trip to toronto in the spring.
That doesn't mean anything. Many things could have altered your gas mileage... Like how you drove the car the first time compared to how you drove it the second time. You might have been going slower, and burned less gas. The other time you might have been going faster and burned more gas. And that is a likely thing to do, if your repeating the same route, since you know where to go.:wink: Hey... If you think you can prove me wrong though, keep trying. But you won't go no where.
AutoTech1
03-04-2006, 03:03 PM
How about this? New cars benefit little from higher than user's manual specified octane no. but old cars benefit more. In my experience, new cars do not knock/misfire often(knocking will automatically result in low efficiency). Old and badly maintained cars knock more often and so they stand to benefit from higher octane no. fuel:smile:.
I would never use a higher octane on a older car... Again, you're just wasting your money... Either get a tune-up (which should target or solve the problem) or get a newer model year car. Engine's wear... Timing changes, rings wear, aluminum parts break down so on and so forth. That knocking is most likely a result of a car that's gone bad after years.:help:
Acetone only destroys rubber, hoses and perhpas plastics, can it harm the engine or other parts itself?
I would never use a higher octane on a older car... Again, you're just wasting your money... Either get a tune-up (which should target or solve the problem) or get a newer model year car. Engine's wear... Timing changes, rings wear, aluminum parts break down so on and so forth. That knocking is most likely a result of a car that's gone bad after years.:help:
For now, I will not rule out using higer octane fuel in old cars as a short term measure. Maintenance is the ultimate solution if a new purchase is out of the question for one reason or another. Let's hear more comments from our knowledgeable fellow members. I am sure there are very well qualified people among us.
Use what is recommanded in your user manual...
http://autorepair.about.com/od/enginefuelgasolines/a/highoctanegas.htm
I refer to my previous post and the link recommended by Gabl above(Thanks Gabl!).
I am not here to convince anyone to use higher octane fuel on old and not so well maintained cars(NB: more old than new cars are not too well maintained because of lack of warranty and regular attention or willingness of the owners to invest further money in them; lots of exceptions exist though). I do not think I ever can.
Yet, I wish to point out that I have based my comments on the paragraph under "Should You Ever Switch to A Higher Octane Gasoline?" of the linked article. Obviously, the writer thinks it is o.k. to try using higher octane fuel first when knocking is detected on a car (on which the user's manual recommended grade of fuel is already in use). If the problem persists, then he reommends to have the car repaired or tuned up, which is utterly logical.
AutoTech1
03-05-2006, 05:47 PM
Acetone only destroys rubber, hoses and perhpas plastics, can it harm the engine or other parts itself?
I was thinking it could do that too, but I wasn't sure. It sounds like some alcohol. Is that what it is?:confused:
As for the engine, I don't think so...
AutoTech1
03-05-2006, 05:49 PM
For now, I will not rule out using higer octane fuel in old cars as a short term measure. Maintenance is the ultimate solution if a new purchase is out of the question for one reason or another. Let's hear more comments from our knowledgeable fellow members. I am sure there are very well qualified people among us.
Don't get me wrong. I agree that using higher octane on a older car would work. I understand what you're getting at.:wink: But I just wouldn't do it. I'd rather get a newer car.:redface:
I was thinking it could do that too, but I wasn't sure. It sounds like some alcohol. Is that what it is?:confused:
As for the engine, I don't think so...
No. Acetone is what they use for paint thinner, nail polish remover, etc.
What is supposedly does in the engine is make the water is the gasoline come apart easier, making the engine able to burn the fuel more completely.
Alcohol, which is water based, would do the exact opposite.
AutoTech1
03-06-2006, 08:58 PM
No. Acetone is what they use for paint thinner, nail polish remover, etc.
What is supposedly does in the engine is make the water is the gasoline come apart easier, making the engine able to burn the fuel more completely.
Alcohol, which is water based, would do the exact opposite.
Thanks.
I don't think I'd use it though... Rubber seals and stuff... Ahhhh... Doens't sound pretty.:redface:
If it actually does anything to them. The person who wrote the website stated that he has soaked hoses and other parts in up to a 20% acetone/ 80% gasoline solution for months, and has seen no adverse affect except in the highest concentration he used to test that theory. Considering 3 ounces to 10 gallons is a .002 % concentration.
AutoTech1
03-07-2006, 04:54 PM
If it actually does anything to them. The person who wrote the website stated that he has soaked hoses and other parts in up to a 20% acetone/ 80% gasoline solution for months, and has seen no adverse affect except in the highest concentration he used to test that theory. Considering 3 ounces to 10 gallons is a .002 % concentration.
Yeah true... You do make a good point.:rolleyes:
DollaZo
05-29-2006, 01:15 PM
sup all
just letting you all know that when I first got my Yaris 1.5L i thought that if I had put expensive fuel in the car that it would benefit my car. 91 octane being cheaper than 98 which is what I put for about 3 months. After a while I started to notice that the car was being harder to drive in terms of playing with the accelerator and the clutch. After speaking to a family friend he recomended me to start using 91 octane. Instantly I noticed that the car was easier to drive, it felt as if the car was happier to drink 91 than 98. So in my opinion I would not recomend using 98 octane as the car was made to run with 91.
SophieSleeps
05-30-2006, 12:19 AM
sup all
just letting you all know that when I first got my Yaris 1.5L i thought that if I had put expensive fuel in the car that it would benefit my car. 91 octane being cheaper than 98 which is what I put for about 3 months. After a while I started to notice that the car was being harder to drive in terms of playing with the accelerator and the clutch. After speaking to a family friend he recomended me to start using 91 octane. Instantly I noticed that the car was easier to drive, it felt as if the car was happier to drink 91 than 98. So in my opinion I would not recomend using 98 octane as the car was made to run with 91.
Yeah. that makes no sense.
Octane is a rating of how resistant the car is to detonation.
running higher octane will have no effect on the car.
The stock ECU will not continue to advance timing blindly if you put in higher octane fuel.
If it is tuned for a 91 octane, you should use no less than 91. However, any more than 91 octane will not make any difference unless you have some serious engine mods and have pushed tuning to a different threshold for knock.
It's funny to see what people say about Octane.
I always hear people talking about how their car runs better on higher octane, or how some people occasionally fill up on higher octane to clean the fuel system or whatever. I laugh silently becuase it takes too long to explain to them that they are clueless.
It's also like when people put on an intake and they say "I can definatley feel a difference. the car is much more powerful"
fearturtle44
05-30-2006, 11:31 AM
It is amazing that people still believe running a higher octane does something tremendous for their engines. It does nothing. You might as well spend the extra $$$ on lottery tickets.
Kevin
SophieSleeps
05-30-2006, 11:33 AM
It is amazing that people still believe running a higher octane does something tremendous for their engines. It does nothing. You might as well spend the extra $$$ on lottery tickets.
Kevin
Thank god someone else on this forum makes sense.
Maybe someday people will learn.
I'm liking the lottery tickets idea.
Actually, that is not true.
1. Gas companies put their best additives only in the highest octane gas, so it can have a cleaning out type of effect.
2. Car companies do all their testing on a car using the highest octane available, especially the gas mileage test. Their must be a reason.
3. It has been noted that higher octane fuel will give better mpg results, however, at this moment the cost of the higher priced fuel outweighs the mpg gains of the better fuel.
4. Running octane lower than recommended will usually destroy a vehicle pretty quickly. Gee, I wonder why.
SophieSleeps
05-30-2006, 02:58 PM
Actually, that is not true.
1. Gas companies put their best additives only in the highest octane gas, so it can have a cleaning out type of effect.
2. Car companies do all their testing on a car using the highest octane available, especially the gas mileage test. Their must be a reason.
3. It has been noted that higher octane fuel will give better mpg results, however, at this moment the cost of the higher priced fuel outweighs the mpg gains of the better fuel.
4. Running octane lower than recommended will usually destroy a vehicle pretty quickly. Gee, I wonder why.
You've been listening to too many people who have been perpetuating rumors.
1. Which additives do they put in? What do they do? I think it sounds like you are reaching on your comment. What is the "best additive"?
2. Car companies may test cars with high octane gas, but only to create a tune that is safe. Once it is safe, they run it at the recommended octane. This is standard. It would be dumb to run it the other way around.
3. It has been noted by stupid people that higher octane gives better mileage. What is the reasoning behind this?
4. Running lower octane gas than recommended can definately do damage to a vehicle. It's because the vehicle is experiencing detonation or pre-ignition due to the octane being too low for the tune.
When you say "pretty quickly" it tells me that you have no idea what you are talking about. Detonation and pre-ignition, when bad enough destroys a motor instantly. A car's knock sensors and knock retard system can accomodate some of this. It will likely throw a check engine light. There is no sort of "damage over time" concept.
Running lower than recommended fuel for 2 months is the same as running it for 2 days. It doesn't do any sort of "gradual" damage. If it is bad enough, it will do instantaneous damage. Otherwise, the knock system is compensating and retarding timing enough that it wont.
bigsky2
05-30-2006, 05:21 PM
Can we clarify a few issues:
- Higher Octane Gas is more resitant to DETONATION
True or False?
- Higher Octane Gas burns more easily than lower octanes
True or False?
I was led to believe that higher octane gas will NOT provide better mileage because the fuel is burning at a higher rate than lower octane, thus using more gas throughout the process.
I'm still confused as to which octane to use, because. the manual states it accepts 87 octane (Research Octane 91).
I've been using 89 Octane from Chevron in Canada.
SophieSleeps
05-30-2006, 05:27 PM
Can we clarify a few issues:
- Higher Octane Gas is more resitant to DETONATION
True or False?
- Higher Octane Gas burns more easily than lower octanes
True or False?
I was led to believe that higher octane gas will NOT provide better mileage because the fuel is burning at a higher rate than lower octane, thus using more gas throughout the process.
I'm still confused as to which octane to use, because. the manual states it accepts 87 octane (Research Octane 91).
I've been using 89 Octane from Chevron in Canada.
Octane is a rating that determines the resistance to detonation.
Higher octane is more resistant to detonation.
It has nothing to do with burn rate...nor mileage. The same amount of fuel goes in.
bigsky2
05-30-2006, 05:32 PM
So the burn rate, if you will, is the same across all octanes?
Then why... are there arguments that higher octane or lower octane provide better/worse mileage...
SophieSleeps
05-30-2006, 05:48 PM
So the burn rate, if you will, is the same across all octanes?
Then why... are there arguments that higher octane or lower octane provide better/worse mileage...
Because they are stupid.
Mileage is determined by how much fuel you use.
How much fuel you use is determined by your air/fuel ratio.
Air/fuel ratio is measured from your primary 02 sensors in your exhaust.
In closed loop operation, your car reads this Air/Fuel ratio and makes adjustments to injector duty cycle.
If your injector duty cycle is higher, you inject more fuel. If lower, less.
Running different octane has no effect on your air/fuel ratio.
Why? Because the ratio is AIR and FUEL.
So naturally it will have no effect on mileage.
If at all, I would think lower octane fuel would be better gas mileage because it is more likely to burn. Then you would have less unburnt fuel exiting via your exhaust. With higher octane fuel, it is less likely to pre-ignite or detonate so you have more a chance of getting unburnt/unused fuel (waste)
bigsky2
05-30-2006, 06:04 PM
If at all, I would think lower octane fuel would be better gas mileage because it is more likely to burn. Then you would have less unburnt fuel exiting via your exhaust. With higher octane fuel, it is less likely to pre-ignite or detonate so you have more a chance of getting unburnt/unused fuel (waste)
Understood and noted SophieSleeps; good explanation on the AIR/FUEL issue.
I'm slightly confused about your last point, because again, I was informed that lower octane fuel could (strong emphasis on could) provide for better fuel mileage because it is not burning as fast as a higher octane fuel.
However, you have stated that it burns more easily, and it relates to your statement about the AIR/FUEL mixture.
I'm just getting conflicting information, and I'm trying to make sure I get my information straight :help:
BTW, it's ok if you don't feel like you need to explain any further, I am enough of a go-getter to do some research in the mean time :redface:
SophieSleeps
05-30-2006, 06:10 PM
Understood and noted SophieSleeps; good explanation on the AIR/FUEL issue.
I'm slightly confused about your last point, because again, I was informed that lower octane fuel could (strong emphasis on could) provide for better fuel mileage because it is not burning as fast as a higher octane fuel.
However, you have stated that it burns more easily, and it relates to your statement about the AIR/FUEL mixture.
I'm just getting conflicting information, and I'm trying to make sure I get my information straight :help:
BTW, it's ok if you don't feel like you need to explain any further, I am enough of a go-getter to do some research in the mean time :redface:
Well...I have not made any reference to burn rates yet...only the likelyness that it will ignite.
Burn rate aside...
Lower octane is more likely to ignite.
Go-getting is good.
If you find more info on octane...let us know.
A word of advice. Be choosy about what you read and take as fact.
A lot of people on forums perpetuate rumors...and they don't provide reasoning.
bigsky2
05-30-2006, 06:20 PM
Ok, so after visiting two stupid proof sites, I discovered the following:
The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.
From HowStuffWorks http://auto.howstuffworks.com/question90.htm
I then went to Wikipedia, which has a very thorough analysis of "Octane Rating" and I found this:
It might seem odd that fuels with higher octane ratings burn less easily, yet are popularly thought of as more powerful. The misunderstanding is caused by confusing the ability of the fuel to resist compression detonation (pre-ignition = engine knock) as opposed to the ability of the fuel to burn (combustion). However, premium grades of petrol often contain more energy per litre due to the composition of the fuel as well as increased octane.
Complete article at: http://en.wikipedia.org/wiki/Octane_rating
Tankota
05-30-2006, 07:26 PM
Ahhh.. Thank you.. somebody who knows their stuff on gas.. I don't know how many times I've had to try and explain octane to people, and that they only need to run what's spec'd by the manufacture, unless the engine is modified. And I have yet to see one bit of hard proff that running higher octane gas in a lower octane engine provides any power or milage gains (which goes against the logic) Almost all have has some faulty testing or just "well, my uncle Joe says..."
One point I'd like to add - the energy in both normal gas and high octane gas is the same, there is no added energy in high octane gas. thus no added power or milage. It only resists ignition at higher compression rates. Once either gas is ignited they both release the same amount of energy.
Well...I have not made any reference to burn rates yet...only the likelyness that it will ignite.
Burn rate aside...
Lower octane is more likely to ignite.
Go-getting is good.
If you find more info on octane...let us know.
A word of advice. Be choosy about what you read and take as fact.
A lot of people on forums perpetuate rumors...and they don't provide reasoning.
SophieSleeps
05-30-2006, 07:31 PM
Ahhh.. Thank you.. somebody who knows their stuff on gas.. I don't know how many times I've had to try and explain octane to people, and that they only need to run what's spec'd by the manufacture, unless the engine is modified. And I have yet to see one bit of hard proff that running higher octane gas in a lower octane engine provides any power or milage gains (which goes against the logic) Almost all have has some faulty testing or just "well, my uncle Joe says..."
One point I'd like to add - the energy in both normal gas and high octane gas is the same, there is no added energy in high octane gas. thus no added power or milage. It only resists ignition at higher compression rates. Once either gas is ignited they both release the same amount of energy.
I love you.
You too bigsky2.
Now if the rest of the world would get a clue.
bigsky2
05-30-2006, 07:33 PM
Higher octane gives better mileage, in a world where people have no clue.
silverRS
05-30-2006, 08:04 PM
yeah im using an Ethanol blend rated at 89 octane wich is just right for the Yaris, the manual at least the Canadian one suggests using Ethanol blends.
SophieSleeps
05-30-2006, 08:19 PM
yeah im using an Ethanol blend rated at 89 octane wich is just right for the Yaris, the manual at least the Canadian one suggests using Ethanol blends.
That is actually one thing that may decrease your gas mileage...since ethanol decreases combustability of gasoline...
I think all of Canada is on some sort of Ethanol/gas mix right?
fearturtle44
05-30-2006, 08:38 PM
Can we clarify a few issues:
- Higher Octane Gas is more resitant to DETONATION
True or False?
- Higher Octane Gas burns more easily than lower octanes
True or False?
I was led to believe that higher octane gas will NOT provide better mileage because the fuel is burning at a higher rate than lower octane, thus using more gas throughout the process.
I'm still confused as to which octane to use, because. the manual states it accepts 87 octane (Research Octane 91).
I've been using 89 Octane from Chevron in Canada.
Not sure if Canada octane numbers are different than US but in the US you only need to run the lowest/cheapest gas which is 87 octane.
Kevin
You've been listening to too many people who have been perpetuating rumors.
1. Which additives do they put in? What do they do? I think it sounds like you are reaching on your comment. What is the "best additive"?
2. Car companies may test cars with high octane gas, but only to create a tune that is safe. Once it is safe, they run it at the recommended octane. This is standard. It would be dumb to run it the other way around.
3. It has been noted by stupid people that higher octane gives better mileage. What is the reasoning behind this?
4. Running lower octane gas than recommended can definately do damage to a vehicle. It's because the vehicle is experiencing detonation or pre-ignition due to the octane being too low for the tune.
When you say "pretty quickly" it tells me that you have no idea what you are talking about. Detonation and pre-ignition, when bad enough destroys a motor instantly. A car's knock sensors and knock retard system can accomodate some of this. It will likely throw a check engine light. There is no sort of "damage over time" concept.
Running lower than recommended fuel for 2 months is the same as running it for 2 days. It doesn't do any sort of "gradual" damage. If it is bad enough, it will do instantaneous damage. Otherwise, the knock system is compensating and retarding timing enough that it wont.
1. How the heck would I know. That is prolly one of the most highly guarded secrets by each oil company.
2. You misunderstand. Car companies use the highest octane gas to supply MPG ratings to consumers. I believe the EPA does as well, I read this somewhere and I can't remember, and for some reason the Fuel economy guide (http://www.fueleconomy.gov/feg/feg2000.htm) omits completely how they test cars.
3. It has been noted in testing that higher octane gives better gas mileage. The latest simple test was by a journalist and it is on a thread somewhere on the board.
4. Yawn. Oh no, I said something you didn't like, therefor I must not know anything. :wink: Yea, if you say so.
And you are again simply wrong about lower octane fuel causing instant destruction. What you are saying is the second a little bit of lower than recommended octane fuel enters an engine it will blow up. That of course is just wrong. An ecu can deal with lower than needed octane for a while, but that will prolly cause detonation, etc. Not all detonation causes the engine to catastrauphically blow up, most detonation just slowly weakens the engine. That is why old cars backfire more than just once.
BTW, as you have noted higher octane gas resists blowing up until the engine wants it too. That is why you can get better power and mpg out of it. Lower octane blows up whenever it feels like.
SophieSleeps
05-31-2006, 02:27 PM
1. How the heck would I know. That is prolly one of the most highly guarded secrets by each oil company.
2. You misunderstand. Car companies use the highest octane gas to supply MPG ratings to consumers. I believe the EPA does as well, I read this somewhere and I can't remember, and for some reason the Fuel economy guide (http://www.fueleconomy.gov/feg/feg2000.htm) omits completely how they test cars.
3. It has been noted in testing that higher octane gives better gas mileage. The latest simple test was by a journalist and it is on a thread somewhere on the board.
4. Yawn. Oh no, I said something you didn't like, therefor I must not know anything. :wink: Yea, if you say so.
And you are again simply wrong about lower octane fuel causing instant destruction. What you are saying is the second a little bit of lower than recommended octane fuel enters an engine it will blow up. That of course is just wrong. An ecu can deal with lower than needed octane for a while, but that will prolly cause detonation, etc. Not all detonation causes the engine to catastrauphically blow up, most detonation just slowly weakens the engine. That is why old cars backfire more than just once.
BTW, as you have noted higher octane gas resists blowing up until the engine wants it too. That is why you can get better power and mpg out of it. Lower octane blows up whenever it feels like.
Prove your statements instead of saying...i read it somewhere, or I don't know because it is a secret of the gas companies.
Maybe I'm making things worse by arguing, but someday hopefully you will actually learn about gasoline and octane. A few people in this thread went on their own to research octane and have found the truth.
You continue to push a baseless argument.
Don't mean to be an ass. Fer serious. If I come off like one, then sorry.
But really. Take a few moments and do some research on this.
You don't know anything about detonation.
Severe detonation does cause the motors to break. Minor detonation doesn't weaken anything. It is a symptom of an impending problem.
True, if you put lower octane fuel in a car, it's not going to all of a sudden break. ECU's are smart enough nowadays that they will retard timing to control knock. If the knock gets bad enough, I believe most cars will go into some sort of "limp" mode and throw a check engine light.
If modern cars did not have this, and you did put lower octane gas in the car, you will absolutely blow the motor.
Backfire is caused by deposits that form hotspots that ignite unburned fuel. A lot of older cars did this because they used leaded fuel which left dense lead residue which retained heat rather well.
Where are you getting your info?
argylesocks
08-08-2006, 10:46 AM
i just checked with the toyota chat line... they said for US, they recommend 87 octane for all Yaris.
TRD_Yaris
08-08-2006, 10:50 AM
do you guys have 87 or 89?? here in texas we get 93 octane as premium, but i can't remember what the regular unleaded is..
07WYarisRS
08-08-2006, 11:32 AM
Rule of thumb is use only the octane needed to prevent knock (detonation)
Anything higher then that and you lose HP and mpg. BUT
Most of these rumors about high octane fuels do not even apply to modern EFI engines. Carbureted engines only folks...
First off burn rates between high octane and low octane can be and often are the same. The difference is the flash point.
Flash point is the temp the fuel is ignited. With too much heat (compression) the fuel will be ignited before the spark plug ignited the mixture and that causes pre-ignition and detonation.
Most factory cars out there can run on low octane, some recommend higher octane for turbo and supercharged cars. With EFI cars today the ECU uses readings from sensors like the o2 sensors and knock sensors. If the engine starts to knock because of low octane or even high loads using high octane it does two things. #1 it pulls the timing. #2 adds more fuel.
With a carbed engine the engine would just knock until it fell apart...
With EFI systems there is no need to run a higher octane fuel unless you running crazy compression and high boost levels.
WFT is the point of building an econo box that requires the most expensive octane fuel. Give your head a shake people...
FWIW high octane fuels do not have more additives.
They contain fewer additives that promote detonation.
Octane boosters do not add octane. Most only but up the rating 3-7 points witch is less then one octane level. Octane booster do however contain additives the remove or neutralize free radicals in the fuel that promote detonation and pre-ignition.
It’s the additives in fuels that change the burn rates not the octane.
These engine were designed to use 87 octane here in North America, anything over that you are wasting your $$$ and lining the pockets of the oil companies. Not to mention doing exactly the opposite of what the car was designed to do SAVE $$$ and be efficient
When you add high octane to an EFI car right away the car is going to run slightly rich as the higher flash point fuel is not going to burn as efficiently, so the ECU using the reading from all the sensors will adjust the timing and fuel trims to burn at the proper mixture (stoich) Regardless what fuel you use running stioch will produce the same HP and KPG
So doing so you end up with the same HP and MPG but less $$$ in your pocket at the end of each week
argylesocks
08-08-2006, 11:50 AM
do you guys have 87 or 89?? here in texas we get 93 octane as premium, but i can't remember what the regular unleaded is..
here in new england
regular = 87
midgrade = 89
premium = 93
SophieSleeps
08-08-2006, 03:46 PM
Rule of thumb is use only the octane needed to prevent knock (detonation)
Anything higher then that and you lose HP and mpg. BUT
Most of these rumors about high octane fuels do not even apply to modern EFI engines. Carbureted engines only folks...
First off burn rates between high octane and low octane can be and often are the same. The difference is the flash point.
Flash point is the temp the fuel is ignited. With too much heat (compression) the fuel will be ignited before the spark plug ignited the mixture and that causes pre-ignition and detonation.
Most factory cars out there can run on low octane, some recommend higher octane for turbo and supercharged cars. With EFI cars today the ECU uses readings from sensors like the o2 sensors and knock sensors. If the engine starts to knock because of low octane or even high loads using high octane it does two things. #1 it pulls the timing. #2 adds more fuel.
With a carbed engine the engine would just knock until it fell apart...
With EFI systems there is no need to run a higher octane fuel unless you running crazy compression and high boost levels.
WFT is the point of building an econo box that requires the most expensive octane fuel. Give your head a shake people...
FWIW high octane fuels do not have more additives.
They contain fewer additives that promote detonation.
Octane boosters do not add octane. Most only but up the rating 3-7 points witch is less then one octane level. Octane booster do however contain additives the remove or neutralize free radicals in the fuel that promote detonation and pre-ignition.
It’s the additives in fuels that change the burn rates not the octane.
These engine were designed to use 87 octane here in North America, anything over that you are wasting your $$$ and lining the pockets of the oil companies. Not to mention doing exactly the opposite of what the car was designed to do SAVE $$$ and be efficient
When you add high octane to an EFI car right away the car is going to run slightly rich as the higher flash point fuel is not going to burn as efficiently, so the ECU using the reading from all the sensors will adjust the timing and fuel trims to burn at the proper mixture (stoich) Regardless what fuel you use running stioch will produce the same HP and KPG
So doing so you end up with the same HP and MPG but less $$$ in your pocket at the end of each week
^ someone who knows his stuff.
I hate it when people use high octane gas in their cars and claim they "feel" a difference. I feel bad for them.
I don't necessarily agree about higher octane = loss of power and fuel efficiency. What is your reasoning behind that?
07WYarisRS
08-08-2006, 05:33 PM
^ someone who knows his stuff.
I hate it when people use high octane gas in their cars and claim they "feel" a difference. I feel bad for them.
I don't necessarily agree about higher octane = loss of power and fuel efficiency. What is your reasoning behind that?
Again that's directed more towards NON fuel injected cars/engines.
A fuel that has a high flashpoint will not ignite as quickly and in a engine that can't compensate by adjusting the timming or fuel delivery that's going to cause a slightly rich mixture as it takes longer to ignite. And we all know the leaner your engine runs the more HP it can make. A sign that an engine is getting more fuel then it needs is carbon build up and even black smoke from the exhaust. This unburnt fuel kills the cat convertors quickly and reduces HO even more over time by choking off exhaust ports and build up in ring lands causing premature wear and blocked oil flow.
With an EFI system the car can make the adjustments needed to correct the fuel/air mixture to some extent.
This is why most Etest places recommend NOT using high octane fuel...
I've been building racing ATV/ motorcycle engines for years and have tested several different fuels and oil on the dyno as well as CHT and EGT gauges (cylinder head temp & exhaust gas temp).
If you set up a carbureted engine to run at WOT at say 1250 degrees on 87 octane, then run that same engine on 94 it's going to drop the egt slightly like 1210-1230 and that just means that you are missing out on HP. In most cases I am able to drop down a size or two on the main jet to gain back the HP and still be at safe operating EGTs.
The computer in a efi car will do the same to compensate by adjusting the fuel trims to lean it out and correct the fuel mixture to restore the hp.
Even at cruise speeds when the A/F mixture is cycling back and forth between too rich and too lean you are missing out on some HP.
Toyota's new ECU programming and use of wideband O2 sensors allow for a much more accurate air/fuel mixture. Instead of cycling back and forth between rich and lean like the old systems they are able to maintain a much closer mixture to stoich with out bouncing back and forth from one extreme to the next.
But like I said no matter what octane you use in your car the ECU/injectors etc will deliver a mixture as close as possible to Stoich and regardless what octane is used the engine with a perfect fuel air mixture and correct timing will not knock.
The only time a person needs to worry about knock and may want to think about using a higher octane is if knock is occuring at steady speeds under normal loads. Many times a higher octane is not even needed, you can just switch brands of fuel. If a higher octane is needed go up 2 points. eg 87-89. There is never any need to jump from 87-91-94 unless you have bumped up the compression an extra 50 psi. An engine like ours that is designed to run 87 and is suffering from detonation will not need more then 89 if it does you have a serious problem.
Occasionally our engines will experiance light ping/knock (spark knock/detonation) a bit under heavy loads but this is no cause for concern, it simply means our engines are operating efficiently.
sroberts
08-08-2006, 06:59 PM
Here in Denver, CO we have 85,87 and 91 octane. Since we are at a higher altitude it is recommended by the dealer to run the 85. You only need to run higher octane on higher compression engines.
SophieSleeps
08-08-2006, 08:02 PM
Again that's directed more towards NON fuel injected cars/engines.
A fuel that has a high flashpoint will not ignite as quickly and in a engine that can't compensate by adjusting the timming or fuel delivery that's going to cause a slightly rich mixture as it takes longer to ignite. And we all know the leaner your engine runs the more HP it can make. A sign that an engine is getting more fuel then it needs is carbon build up and even black smoke from the exhaust. This unburnt fuel kills the cat convertors quickly and reduces HO even more over time by choking off exhaust ports and build up in ring lands causing premature wear and blocked oil flow.
With an EFI system the car can make the adjustments needed to correct the fuel/air mixture to some extent.
This is why most Etest places recommend NOT using high octane fuel...
I've been building racing ATV/ motorcycle engines for years and have tested several different fuels and oil on the dyno as well as CHT and EGT gauges (cylinder head temp & exhaust gas temp).
If you set up a carbureted engine to run at WOT at say 1250 degrees on 87 octane, then run that same engine on 94 it's going to drop the egt slightly like 1210-1230 and that just means that you are missing out on HP. In most cases I am able to drop down a size or two on the main jet to gain back the HP and still be at safe operating EGTs.
The computer in a efi car will do the same to compensate by adjusting the fuel trims to lean it out and correct the fuel mixture to restore the hp.
Even at cruise speeds when the A/F mixture is cycling back and forth between too rich and too lean you are missing out on some HP.
Toyota's new ECU programming and use of wideband O2 sensors allow for a much more accurate air/fuel mixture. Instead of cycling back and forth between rich and lean like the old systems they are able to maintain a much closer mixture to stoich with out bouncing back and forth from one extreme to the next.
But like I said no matter what octane you use in your car the ECU/injectors etc will deliver a mixture as close as possible to Stoich and regardless what octane is used the engine with a perfect fuel air mixture and correct timing will not knock.
The only time a person needs to worry about knock and may want to think about using a higher octane is if knock is occuring at steady speeds under normal loads. Many times a higher octane is not even needed, you can just switch brands of fuel. If a higher octane is needed go up 2 points. eg 87-89. There is never any need to jump from 87-91-94 unless you have bumped up the compression an extra 50 psi. An engine like ours that is designed to run 87 and is suffering from detonation will not need more then 89 if it does you have a serious problem.
Occasionally our engines will experiance light ping/knock (spark knock/detonation) a bit under heavy loads but this is no cause for concern, it simply means our engines are operating efficiently.
That's a mouthful. I didn't know you were referring to carb'd cars with that comment.
dbaxter
08-18-2006, 10:38 PM
Dont think you should be running 100 octane, I only use that when going to the dragstrip in my SS or GTO, just less chances of running on the low octane tables and less chance of knock.
I have been running the it on the lowest regular octane at any of the stations. Truthfully not careing as long as it was cheap. Runs great and getting the advertised 32 mph city. I am sure yanking the spare and putting in the CIA will help more then anything else, header and tuning also.
riceboy
08-19-2006, 11:49 PM
Just put in the cheap stuff and drive...
wwwh355
08-22-2006, 08:58 PM
Unless you are experiencing rough running or misfires, then odds are the car would not run smoother.
In case of misfires, I thought u should get lower octane rated fuel which is "easier" to fire.
mikeukrainetz
08-23-2006, 06:53 PM
Lower octane gas will fire with less compression, if its misfiring or pinging the gas is lighting up well before TDC, higher octane will bring the flashpoint back up to prevent this. Ive found this really only happens on older vehicles where the timing (among everything else) is old and worn. Carbon buildup can cause this as well. High compression engines (60's-70's and less so 80's and rebuilt hi-po engines) require higher octane to prevent detonation and literal meltdown. What I dont really understand is in the scheme of things the Yaris is a high compression engine - it runs at 10.5:1 and can run on 87 octane... my 70 chev with a built 350 runs 10.25:1 and I cant get away with anything less than 91... it doesnt have aluminum heads but I never understood why one works and the other doesnt....
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