What grade of gas? All gas questions answered! **Merged all gas threads**

[jasonandre]

Only long-term use of regular would cause any possibility of damage. Like they said, just top-off with Premium and you'll be fine.

[GeorgiaBoy]

add an octane booster from the parts store. That is jet fuel and can raise the octane level faster tham just adding premium. Same stuff is in fuke injector cleaners as well.

[ScorchedHands]

What is the advantage of this? I'll admit I don't know much about why there are different octane levels of fuel. I know the basics, but I would love to learn more about this.

[twistedframe]

higher octane gas burns longer, so you get complete combustion and it is less likely to spontaniously combust (which is aka detonation). By complete combustion i mean there is no more of the a/f mixture left in the cylinders, therefore there is nothing that can combust.

[twistedframe]

The ideal gas law tells us that a gas heats up when compressed, therefor if you compress it enough it will combust on its own (that is the basic way a deisel works). That is why a deisel has sometimes 25:1 compression and no spark plugs.

[ScorchedHands]

So this is more of a safety measure than a performance measure. I've heard
that there are performance benefits to higher octane also. Is this true?


I am aware of how diesel works. I guess the idea is to kind of prevent this from happening unexpectedly in a fuel injected engine? Would this mean that diesel fuel has a very low octane?

Also, how does all of this influence gas mileage? I'm just try'n to cover all the bases lol

[twistedframe]

i think it is lower, however deisel is usually rated in cetane. well to me an engine that doesn't knock is perfoming well so to me i see it as a perfomance issue. however its is not a perfomance booster in a car that doesn't call for it.

[ScorchedHands]

What's the easiest way to tell if the engine is 'knocking'? Does it idle differently? Sound different?

I don't think mine is, but I'm curious to learn as much as I can about everything (doesn't just pertain to said subject).

[twistedframe]

you will hear it ticking or maybe louder knocking. also i believe that it will throw a code if the knocking gets bad enough.

[ScorchedHands]

Aparently, I just read, that turbo chargers and super chargers can also cause detonation. And that intercoolers can help to prevent this. hmmm

http://zhome.com/ZCMnL/PICS/detonation/detonation.html


Just branching the subject out to learn more.

[twistedframe]

right since the turbo/supercharger generates so much heat you need to cool the air off before it enters the combusiton chamber. if it wasn't cooled then it would raise the temp of the a/f mixutre and as stated before we all know what happens if gas gets too hot under pressure.

[MyFirstCivic@35]

Originally Posted by webby

twisted frame told you why. Detonation - the compression is high on the SI.

what is detonation:
a condition, in which, after the spark plug fires, some of the unburned air-fuel mixture in the combustion chamber explodes spontaneously, set off only by the heat and pressure of air-fuel mixture that has already been ignited. Detonation, or "knock", greatly Increases the mechanical and thermal stresses on the engine.

I hate to disagree but I may also be talking about a different condition. I had always referred to this condition as predetonation. Which is a condition where the air fuel mixture ignites only by the heat and pressure just prior to the spark plug firing. The knock is then caused by the exploding gasses slamming down on the piston that is still in upward travel. The sound is created at the area where the wrist pin connects to the piston.

[twistedframe]

i think we are talking about the same thing you just went into more detail...i think, i have been known to be wrong though. i thing detonation and predetonation are the same things.

[webby]

here is a site on detonation - check out the info here

http://www.misterfixit.com/deton.htm

[ScorchedHands]

uh webby...check ur link lol

[ChinoiSI]

Originally Posted by webby

does it not say on the gas cap or gas door for the SI? Usually it says "premium Fuel" on the gas area, on the dash sometimes, or on the gas door release. Someone with an SI will have to verify. Don't worry about your tank you have in the car. Just top it off with premium and call it a day. You'll be ok. From now on, I'd just fill with premium though

yepyep it does say premium when u open ur gas Door. haha wutever u wanna call it.

[webby]

Originally Posted by ScorchedHands

uh webby...check ur link lol

sorry I edited it. It's one of those days.

[fhound258]

lol, i always use 93 or higher. but when im really low on money, i got for regular with some octane booster.

[jsal5045]

duh it has big white letter on fuel door. PREMIUM FUEL ONLY SEE OWNERS MANUAL

[ScorchedHands]

like i said... it's always dark when i'm fill'n and i didn't think to look


play nice