Fuel Octane

[MrRline2010]

I was just wondering from time to time can you run something a little higher in a 04 civic lx. For my other cars every once in a while I would put a tank of 91 in. Can you do this on 7th gens

[mcard]

if you feel like paying extra at the pump and not getting anything in return from your car...

[MrRline2010]

eh maybe i'm wrong and most likely I am, but i've always heard every once in a while it's good to run a higher octane for a tank in your car. Not sure if this is fact or myth though.

[02BLKCIVIC]

myth :argue:

[*inFamous*]

The higher the octane rating, the more resistant the gasoline is to combustion, allowing you to run more timing and compression.

If you dont have this timing/compression added to the equation, the end result is the extra money is wasted as its doing exactly the same thing as say... 89 grade octane.

[Rufus]

Your car is effecient with 87. Anything higher is intended for a motor/setup requiring a higher octane rating.

[Tage]

The higher the octane rating, the more resistant the gasoline is to combustion, allowing you to run more timing and compression.

If you dont have this timing/compression added to the equation, the end result is the extra money is wasted as its doing exactly the same thing as say... 89 grade octane.

I'd go so far as to say that you can actually loose power by not running the octane the motor was designed for. For any given motor, you want maximum cylinder pressure at a specific crank angle after TDC. Similar to pedalling a bicycle, you push down as hard as you can just slightly past the top of the crank stroke. If you wait until you're parallel with the ground you're giving up power. The same thing would apply to gasoline if it's burning too slowly (or too fast) and creates max cylinder pressure at a crank angle beyond the optimum (in theory somewhere around 15 degrees after TDC if I recall).

I think back in the day gas didn't have as much anti carbon built up cleaning crap mixed in and there would be so much carbon build up that the compression would actually increase and the engine would start "pinging". The easy fix was to simply put a higher octane fuel in it to make it stop. Back in the day the premium fuel may have had more carbon cleaning stuff mixed in the fuel to help clean up the combustion chambers so running every 3rd tank with premium was a good idea. I don't think it applies these days either.

[*inFamous*]

I'd go so far as to say that you can actually loose power by not running the octane the motor was designed for. For any given motor, you want maximum cylinder pressure at a specific crank angle after TDC. Similar to pedalling a bicycle, you push down as hard as you can just slightly past the top of the crank stroke. If you wait until you're parallel with the ground you're giving up power. The same thing would apply to gasoline if it's burning too slowly (or too fast) and creates max cylinder pressure at a crank angle beyond the optimum (in theory somewhere around 15 degrees after TDC if I recall).

I think back in the day gas didn't have as much anti carbon built up cleaning crap mixed in and there would be so much carbon build up that the compression would actually increase and the engine would start "pinging". The easy fix was to simply put a higher octane fuel in it to make it stop. Back in the day the premium fuel may have had more carbon cleaning stuff mixed in the fuel to help clean up the combustion chambers so running every 3rd tank with premium was a good idea. I don't think it applies these days either.


Pretty much summed up the theory man.

If your car is setup for 91, use it, if not, dont!

[MrRline2010]

Thanks for the info tage and teggie

[Tweeder]

GSRs have to use 91 right?

[Tage]

If you want max performance, yes.

Do you HAVE to, no.

GSR's have a knock sensor so if you use crappy gas it will pull timing to reduce/eliminate the detonation. I wouldn't purposely put in 87 octane but I've actually driven across country and the gas selection was 85, 87 and 89. Conversely, I've been places were the 3 pump choices were 89, 91, and 93 and if I recall correctly I believe some parts of TX had 94!

It's not 91 specific, it's run the highest octane that's available at the pump if it says "Premium Fuel Only" on your gauge cluster.

[MrRline2010]

your correct in texas tage nothing lower than 89 atleast when I was going from san antonio to el paso there wasn't

[Rufus]

Conversely, I've been places were the 3 pump choices were 89, 91, and 93 and if I recall correctly I believe some parts of TX had 94!

It's not 91 specific, it's run the highest octane that's available at the pump if it says "Premium Fuel Only" on your gauge cluster.

I flew to Texas to pick up a boosted IS300 years ago that was tuned on 93. Came back to AZ and no 93 to put in it. Thankfully, it had alcohol injection and there were PLENTY of Home Depots to stop at between here and Dallas.

[kos]

yeah tage and ravi basically summed that up lol