Don't use premium gas if your car isn't rated for it.

Daso

Daso

New member
Interesting read from another board, he's right and Im not retyping it all up myself. This is the quick collection of info.

Here is the link to the original thread with complete info: http://www.7thgencivic.com/forums/showthread.php?t=203041

This deals with the civic which is rated to use regular gas in the car's manual.

part 1 said:
I'm not sure what kind of expert opinion you are looking for. But if you are running 93 octane, you ARE losing power, and you ARE going to build up crap and contaminants in your engine much quicker. They always say 87 or higher, because of the fact that some places may only offer 88 or 89.

You are wasting money, you are losing power, and you are gonna have a fairly gunked up engine by the time you get up there in mileage.

I'll explain this again since you seemed to have missed the technical explinations. The only thing octane rating is, is resistance to detonation and heat. The higher the octane, the more heat required to get the mixture to ignite.

Hence the reason cars with higher compression engine or turbos require premium. Cars with turbos, etc, and with higher compression tend to have their mixture get much hotter in the combustion chamber before the ignition spark. Using a lower octane gas in a car that requires premium causes premature detonation (which is bad, duh) since the heat detonates the lower octane gas.

Likewise, if you are using higher octane gas in your civic, the mixture may not get hot enough in your combustion chamber to burn completely through. This leaves excess fuel/air mixture in your combustion chamber during the exhaust stroke, causing a loss of power and buildup of excess contaminants. Stop using 93 octane, because you're losing power and you're pissing money away. This also burns your valves and over time you will burn through them.

As for using high octane gas and nitrous, this is somewhat a paradoxical situation. Nitrous can benefit from using higher octane gas, since the oxidization process induced by nitrous causes the mixture to super heat. again higher octane gas is more resistant to heat, therefore will help prevent detonation when spraying.

however, when you're not spraying, you're back into the category above, where it's causing loss of power and excess waste and contaminants.

As for using 100 octane gas in your car, I'd advise against that in a very cautious sense. The addatives in higher octane gas worsens the effect you're seeing here, even if you're using nitrous. Turbos can use it if they crank up their boost to the point that they'd benefit from it. However, most don't do that unless they've been tuned for it, becuase running high octane gas and high boost without being tuned is a very dangerous combination to gamble with.

If you see some ricer in his n/a civic filling up with 100 octane, point and laugh, because everyone else who actually knows what they are doing, will certainly be laughing along with you.


Oh and I found out the thing with the injectors. The addative that they use to give gas its higher octane can cause premature injector failure, injector misfires, etc, if your injectors were not made for that kind of fuel. This is an extreme case and few and far between, but it can happen, and does happen. I have to go back and look, but the addatives cause buildup on the injectors, leading to the above said failures. However, this is not always the case, so really, it's hardly worth mentioning.

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This is SCIENTIFIC FACT! Methanol is completely different than using pump gas. You can't even compare the two.

No, higher octane gas does not burn more cleaner, nor does it burn more completely.

ALL THE OCTANE RATING MEANS IS THAT IT IS MORE RESISTANT TO DETONATION AND HEAT!!!


And as for the person who got better mileage with 89 than 87. Assuming your car isn't FI'd then you did NOT get better mileage just because you used higher octane. There are too many other factors involved to do an experiment like that. The ONLY case where this would be is if your car was detonating for some reason, but you'd get a CEL if something was that majorly wrong.

Also, the whole "well premium gas has more cleaners in it to help your car". wrong. government regulations prevent this. the only difference is the addative used to increase octane rating.

Once again. Higher octane gas is more resistant to heat and detonation. (this also means it takes longer to burn, which is WHY if you DONT have a car set up for premium you'll eventually burn through your valves). If you are going to run premium you have to tune for premium. you would have to advance your timing 2 degrees and retard your exhaust valves in order to allow the mixture to burn through completely before the scavaging of the chamber.

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Here... so you know I'm not talking just "hearsay"

this was in a pdf i found at the american petroleum institute. here are some excerpts. i believe this was also hilighted on the service advisor web site.


WHAT IS OCTANE RATING?

Octane, by definition, is the resistance to burn or detonation. The higher the rating, the slower the burn when ignited during the compression burn cycle of the piston. The higher octane allows for better control of burning for high compression engines. So we want to match the correct octane rating of the gasoline to the engine design to ensure complete burning of the gasoline by the engine for maximum fuel economy and clean emissions.

I THOUGHT GASOLINE WITH HIGHER OCTANE REDUCED ENGINE KNOCK?

It did in older engines using carburetors to regulate air/gas mix They cannot as accurately regulate the air/fuel mix going into the engine as a computerized fuel injector. Carburetors need adjustment, as a part of regular maintenance, to keep the air/fuel mix as accurate as possible. So many times, these adjustments were not made regularly causing too much fuel to be mixed with the air. When this happened the gasoline would not burn completely soaking into carbon deposits. This would cause a premature ignition of the gasoline due to the intense heat in the engine cylinder creating "engine knock." When this happened, people would change to the higher octane/slower burning gasoline to resist the premature burn, thus minimizing the knocking problem. And it worked. Good solution.

However, since the middle to late 80’s, engines are designed to use fuel injectors with computers to accurately control the air/fuel mix under all types of temperature and environment concerns. However the accuracy of the fuel injectors and computers is based on using the recommended gasoline for that engine.

Most cars are designed to burn regular unleaded fuels with an octane rating of 87. If the vehicle needs a higher octane rating of 89-93, there is documentation in the owner’s manual, as well as possibly under the fuel gauge and by the fuel fill hole. Usually you will see this rating for high performance engines only.

WHAT IF I PREFER TO USE GASOLINE WITH HIGHER OCTANE RATINGS?

You can, but there are no real benefits, other than the gasoline manufacturers making more money off of you. When you use a fuel with a higher octane rating than your vehicle requires, you can send this unburned fuel into the emissions system. It can also collect in the catalytic converter. When you over stress any system, it can malfunction or not do what it was designed to do properly. In the early 90's, an early warning symptom was a rotten egg smell from the tailpipe. Easy fix, go back to using regular 87 octane gasoline. The rude odor usually disappears after several tanks of gasoline.

DOESN'T HIGHER OCTANE GASOLINE HAVE MORE CLEANING ADDITIVES THAT ARE GOOD FOR MY ENGINE?

No. Government regulations require that all gasoline contain basically the same amount of additives to clean the injectors and valves. The only differences are the type to help create the different octane ratings. All gasoline burns at the same rate, it is the additives that create the different octane ratings for the different types of engines.


http://auto.howstuffworks.com/question90.htm

And here's from the federal trade commission.
http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm
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Next part due to length constraints on a single post.

part 2 said:
Cars that do not have higher compression have a lower temperature of the mixture before ignition. (this is basic physics... the more you compress air/matter the hotter it gets) So in a car that does not have higher compression, honda builds the car from the factory with the appropriate timing for the recommended octane.

Higher octane gas burns LONGER since it is more resistant to detonation and heat. So the time it takes to burn through the mixture on 87 octane is LESS than what it takes to burn through a mixture with 93 octane.

if your car is setup for 87 octane (like the civic) the 93 octane will not have completely burned through the mixture by the time your combustion chamber has opened the exhaust valves and is scavanging the mixture. This gives the still burning mixture the not-so-great opportunity to burn through your valves since it now has an out and a re-introduction of oxygen via the open exhaust valves. This is what causes the buildup of crap on your valves and other parts which can lead to damage down the road. Also because the mixture did not finish burning, some of that fuel or unburned mixture can go through your exhaust and then settle in your catalytic converter, causing you to fail emissions and/or damage your cat.

So there are 2 keys to having a car that can run premium effectively without these issues. number 1, higher compression, which causes more heat, allowing the mixture to burn more efficiently and more thoroughly with less leftover contaminants.

number 2, advanced ignition timing and retarded exhaust valve timing, allowing the mixture more time to burn with closed valves.

going from 87 to 89 octane isn't too bad, but going from 87 to 93 can be harmful in the long run and cause a loss of power in the short run. (if your mixture burns all the way through, it gives you more power obviously)

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Just for the record, octane rating is this:

pure iso-octanol (the harder to get of the two forms of octanol) is considered to have an octane rating of 100. 87% iso-ocatanol and 13% n-octanol has an octane rating of 87. Every other compound is then measured agianst 100% iso-octanol, for instance methanol, has an octane rating of 104, so it is 104% harder to ignite than iso-octanol.

You see this has little to do with carbon build up. Really it is more like the adative they put in to the fuel, try changing gas stations. But from what I have seen of other peoples pistons on this site, it isn't abnormal. Gearbox had heavy build up after only 20k (i think it was 20K) and he never sprayed or anything (that I know of).

What a company can do is take a low grade fuel, like say 80 octane octanol, and mix 5% methanol (which has an octane rating of 104) and get 87 octane. These addative have are more likely to cause carbon build up. Some of these addative are to raise the octane while other are for the enivroment.

Also keep in mind, methanol is bad, not for your engine but for all the plastic lines and O-rings, Shell uses methanol in their gas.

This is text book stuff, yes I have those text books. I'm a chemical engineer, chemical enginers purpose is to refine oil and work in the petroleum industry.

In the end, just use what gas your manual cars for. Detergents are nice, but your car doesn't require them to run nor will they give noticable power or anything of that nature nor will they clean you engine more (well maybe a little, but you'll never notice the difference).
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I've always known it.

It's fairly noticeable in Saturns, since when using Premium, you lose half mileage, your engine doesn't sound the same or run as good.

That was on my SOHC. Now I have a DOHC, and I notice the difference when not on Premium, as far as acceleration goes.

When I had the SOHC, I had to use only Ultramar, cuz additives weren't helping the engine either..

I guess it's all a trial-error and see what works best for your car.
 
My car required 91 octane gas when it was bone stock.

Now it's turbocharged and it's making almost twice the power it did when it came out of the factory.

So yeah... im using premium gas in my car. :p
 
In the end, just use what gas your manual cars for.
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c'est pas mal tout ce que j'ai trouver d'interessant.

chaque moteur est different et est tuner d'origine de facon differente alors mettre un autre indice d'octane que celui recommander va avoir des effets different sur chaque moteur selon la temperature,la conduite,l'altitude etc... bref ya tellement de variante que c'est facile de ce perdre a faire plusieurs affirmations.

Likewise, if you are using higher octane gas in your civic, the mixture may not get hot enough in your combustion chamber to burn completely through. This leaves excess fuel/air mixture in your combustion chamber during the exhaust stroke, causing a loss of power and buildup of excess contaminants. Stop using 93 octane, because you're losing power and you're pissing money away. This also burns your valves and over time you will burn through them.
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je trouve ca tirer par les cheveux car tout nos moteur on de la misere a bruler tout le gaz sinon a quoi servirait nos catalyseur et notre EGR
 
mustangup said:
je trouve ca tirer par les cheveux car tout nos moteur on de la misere a bruler tout le gaz sinon a quoi servirait nos catalyseur et notre EGR
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Jusqu'a un certain point. Mais ca c'est dans des conditions idéales. On peut produire un mauvaise combustion sans laisser des dépots nocifs pour le moteur. Si l'indice d'octane est trop élevé, c'est probablement la que ca devient pire. Mais j'ai des doutes pour ce qui est des domages graves causés par un indice d'octane trop élevé.
 
endommager un moteur, je crois pas... mais l'octane est un anti-détonnant... si ton moteur détonne pas sur de l'ordinaire et bien reste avec ca.

contrairement a ce que la pluspart des "mononcs qui savent tout" croient, ca nettoie pas le moteur et ca marche pas plus.

Combient de fois j'ai entendu dire "jmet une tank de supreme une fois de temps en temps pour nettoyer le moteur".... allo l'cave, ca nettoie pas.

Le seul qui nettoie le moteur c'est Petro Canada avec leur affaire de Tactrol, mais ca a rien avoir avec l'indice d'octane.

Sur ce, je gaz au 94 chez Petro Canada mais avec 11.3:1 de compression jme risque pas avec de l'ordinaire :)
 
kRANkED said:
endommager un moteur, je crois pas... mais l'octane est un anti-détonnant... si ton moteur détonne pas sur de l'ordinaire et bien reste avec ca.

contrairement a ce que la pluspart des "mononcs qui savent tout" croient, ca nettoie pas le moteur et ca marche pas plus.

Combient de fois j'ai entendu dire "jmet une tank de supreme une fois de temps en temps pour nettoyer le moteur".... allo l'cave, ca nettoie pas.

Le seul qui nettoie le moteur c'est Petro Canada avec leur affaire de Tactrol, mais ca a rien avoir avec l'indice d'octane.

Sur ce, je gaz au 94 chez Petro Canada mais avec 11.3:1 de compression jme risque pas avec de l'ordinaire :)
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corrige moi si je me trompe..mais l'etanhol aussi nettoie le moteur.....

dans mon encien char la premiere fois que j'en ai mis ca a tellement décrassé la tank et la ligne a gaz que mon filtre a gaz(pres du carburateur) a boucher avant que je vide la tank

une fois changé....plus de problemes!!

moi je gaz chez sonic a LeGardeur, l'ethanol est au prix de l'ordinaire en tout temps......une essence intermediere au prix de l'ordinaire yesss!!
 
My friend's dad had a 2000 accord, and his buddy has a 2000 accord aswell. Both not v6. One put supreme from the begining and the other has only put regular. When the guy with regular drove the other accord he said it felt so much newer and better:he could feel the difference". They think its because of the supreme gas, is this dum or what??
 
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mustangup said:
c'est pas mal tout ce que j'ai trouver d'interessant.

chaque moteur est different et est tuner d'origine de facon differente alors mettre un autre indice d'octane que celui recommander va avoir des effets different sur chaque moteur selon la temperature,la conduite,l'altitude etc... bref ya tellement de variante que c'est facile de ce perdre a faire plusieurs affirmations.



je trouve ca tirer par les cheveux car tout nos moteur on de la misere a bruler tout le gaz sinon a quoi servirait nos catalyseur et notre EGR
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Je vais devoir te corriger , l'egr ne sert pas dutout a bruler le pétrole(j'utilise le mot pétrole car certain pourrait confondre le gaz liquide,le fuel , au gaz d'échapement) qui a été non brulé dans la chambre de combustion

Contrairement a ce qu'on croirait, la recirculation de l'egr rempli la chambre de combustion de gaz d'échapement . de cette facon elle abaisse les temperature de la chambre, reduit la production de NoX, peut procurer une économie d'essence et etc etc ...

sa fait drole de penser que des gaz déchapement a ~900˚F peuvent garder une temperature plus basse , mais si on met par exemple 50cc de gaz non brulable a une temperature X, il réchauffe moins la chambre que si on injecterais 50cc de mélange air/essence qui serait brulé et produirais X nombre d'energie et réchauferais la chambre . De plus si on fait entrer moins d'air dans le moteur, on injecte moins d'Essence, ce qui permet d'avoir uen très bonne économie d'essence en cruise et en faible acceleration

Sans offence , je fait juste ajouter des précisions :p
 
ilikeacura said:
My friend's dad had a 2000 accord, and his buddy has a 2000 accord aswell. Both not v6. One put supreme from the begining and the other has only put regular. When the guy with regular drove the other accord he said it felt so much newer and better:he could feel the difference". They think its because of the supreme gas, is this dum or what??
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It can contribute to a lot of things. General Maintence of the Vehicle, and it how it was driven, etc. The ECU learns how you drive the vehicle, and adjusts accordingly. This is why you tend to burn more gas when the vehicle's power is lost. Also the number of kilometers on the car. My brother just took my car out a few days ago, and the only 'modification' to it is that its dropped, and it had a K&N Filter on it. But my car also has 110,000km LESS on the motor (same year vehicle).
 
mustangup said:
je trouve ca tirer par les cheveux car tout nos moteur on de la misere a bruler tout le gaz sinon a quoi servirait nos catalyseur et notre EGR
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En fait, les moteurs ne sont pas conçu pour brûler tout l'essence qui est envoyer. Une grande partie de l'essence envoyé sert seulement à contrôler la vitesse de combustion pour empècher d'avoir une explosion.

Un indice d'octane plus haut va absorber davantage de chaleur et va être "moins détonant", ce qui permet de rapprocher un peu le ratio air/essence du ratio stoich sans avoir d'explosion et sans scraper ton moteur.

Donc si tu n'es pas propice à détonner (ratio de compression bas et ratio A/F bas), mettre un indice d'octane plus haut va absorber plus de chaleur, donc tu vas perdre davantage d'énergie de ta combustion, donc moins de hp. :)
 
bah i never new the exact reason but i only run 91 in my h22 and my civic gets regular 87.

my dad used to run his supra on 87 and never ever had a problem for around 250k when it got stolen.

i think sport compact car even had an article about this a few years back , i might still have the issue
 
tyu said:
manufacturers aren't stupid, just use as stated in the manual
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well...lets not go that far.



personally when i started running supreme in my uber low compression 305 it sounded better and started on a half of a dime
 
Franky said:
En fait, les moteurs ne sont pas conçu pour brûler tout l'essence qui est envoyer. Une grande partie de l'essence envoyé sert seulement à contrôler la vitesse de combustion pour empècher d'avoir une explosion.

Un indice d'octane plus haut va absorber davantage de chaleur et va être "moins détonant", ce qui permet de rapprocher un peu le ratio air/essence du ratio stoich sans avoir d'explosion et sans scraper ton moteur.

Donc si tu n'es pas propice à détonner (ratio de compression bas et ratio A/F bas), mettre un indice d'octane plus haut va absorber plus de chaleur, donc tu vas perdre davantage d'énergie de ta combustion, donc moins de hp. :)
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ce que tu dis n a aucun sens....
reflechis 2 secondes
aussitot que tu deviens trop riche (reste carburant dans gaz exhaust) le O2 sensor le lit et envoie moins de carburant pour toujours rester a 15:1 de ratio stechio.
l octane n absorbe aucune chaleur !!!!!!!!
indice octane plus haut = temperature autoallumage plus haute aucun rapport avec absorber energie ou non
exemple avec chiffres fictifs:
IO = 100 : temp. autoinflammabilité = 200 deg. C
IO = 91 : temp. autoinflammabilité = 188 deg. C

le 100 octane n absorbe pas plus d energie il ne fait que bruler a une temp superieure la meme putain d energie sera crée par les 2 sauf que le IO = 91 detonnera avant le IO = 100

la seule chose qui nuit c est les additifs anti-detonnants qui sont inpures car ne sont pas des hydrocarbures, donc pourrait encrasser, enfin ce ce qui disent
 
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