yamahaSHO

iTrader: (2)

Close, but not totally accurate. Although compression is a factor, it is heat is what you're worried about. Higher octane resists pre-ignition and detonation better. When you compress something, you create heat. If you can get the fuel/air mixture hot enough, it will ignite. With that said, if you go with a higher octane, say 105, and your car runs great with 87, then you are actually likely to lose power as the higher octane will be harder to ignite and burn slower if the temperature is not high enough. You're not likely to do any damage if you use the 105, but you're power and gas mileage may decrease.

In the winter, you have more available oxygen to burn, however, the temperatures are much cooler so higer octane is not needed.

Basically, octane should be related to heat, not so much compression (as heat is created by compression). Aluminum heads, having a clean burning combustion chamber, and being able to expel exhaust (heat), will allow you to run lower octane. 20 years ago, 10:1 or higher was unheard of on a street car that was made to run on low-grade gasoline.

Diesels run on such high octane (diesel fuel) because the create a lot of heat from the compression. They are also MUCH more effecient than a gasoline engine.

ragingSPAM

iTrader: (8)

wow those of you who use anything more than 87 in a stock civic are pretty uninformed...

basically the higher the octane on gas is the harder it is to burn
higher octane gas will not improve mileage or power because if your car is not suited for it than it will have a harder time burning all of the fuel that is in the cylinder...
when an engine compresses an air fuel mixture its usually designed to run on a certain fuel so all of the mixture is burned and you get the most out of the cycle...
but once u put higher octane fuels in the system designed for lower octane fuels it has a harder time burning because its compression isnt creating enough heat to burn all of it when the spark plug ignites so a lot of excess fuel is dumped out but is filtered by the catalytic converter thats why you dont smell it but it still is getting dumped out...it makes your car run rich, and uses up more gas so you're actually getting less gas mileage out of your car...

ronaldo9

iTrader: (6)

Somebody sticky this thread if it already isn't!!!!!

lxcivic2k1

x2 ppl need to know!

enjoitofer

well i put 89 octane when i first got my car but it ran like doo doo then i read the manual then it say should use 92 octane and bla bla bla like that so i been using it ever since and my car works great.

yamahaSHO

iTrader: (2)

Most of that is probably in your head. This motor has great cooling ability considering it is all aluminum. If it was running bad on 89, you probably got bad gas.

I'd give 89 a try again...

gearbox

iTrader: (95)

haha the manual says 87 in a civic, it will give the best mileage and performance. maybe you picked up the manual for dads s2k by mistake

cwo715

iTrader: (13)

yea where in the manual does it say use 92 octane... idk where your at but last time i checked the octane ratings are 87, 89, 91, 93, 97, 102, 108, 119 (which is ethanol based)

yamahaSHO

iTrader: (2)

The octane ratings you're used to are local. You can get other octane ratings here. Our standard 3 here in CO at most gas stations is 85, 87, 91. On the track I use 105.

boricua_civic

haha I used to use 93 but the car was too fast for me

enjoitofer

i live in hawaii well i guess the rating is diferant each state cause we have 87,89,92,100 octane

ragingSPAM

iTrader: (8)

we have some 76 stations which have 100 octane gas...but that usually costs on average of $6.50-8.00 per gallon

yamahaSHO

iTrader: (2)

The higher in altitude you go, the more likely you'll have lower octane at the pump.

SOHC_VTEC_pwr

lets take this to mythbusters!!!

Trezore

From my experience, my ultimate test was to fill the tank several times with 87 octane and 93 octane on my previous Honda cars. 1997 Accord EX (4 cyl), 2008 Accord EX-L (4 cyl), 20011 Accord EX-L (4 cyl), 2009 Civic Coupe EX.
On every single one, testing miles per gallon and performance, I have gotten better mileage using the higher 93 octane.

Now whether or not my heavy foot has anything to do with it, is something to consider as well... I like starting off the line as quickly as possible to get up to speed limit.

Also, I have a friend that is qualified for working on the NSX, and he advised me all Honda cars are built for super, high octane. So I believe him after running my tests using the various octane to see how far I get for the money.

When I calculated the miles per gallon to price per gallon... I actually could SEE if I was losing money or not!!!

People, it is very simple to figure out by calculating your fuel usage.
Sample:
$2.00 per gallon for regular (87) ... say I filled tank after 217 miles. that's 22 mpg
$2.50 per gallon for super (93) ... say I filled tank after 257 miles, that's 27 mpg
40 mile difference 40/2.5= $16 , 40/2 = $20
I saved $4.00!!!! not a lot, but still a savings!!!! it adds up over time!!!