I thought the same thing a while ago. I tried an experiment, forever I used like 86 octane in my beater Mazda 323, then I put in the highest grade which was around 91 or so.

Anyway, I got like 30 more miles out of my tank and I did notice a slight difference in performance it ran smoother.

What I've been hearing is that higher octane will have a much greater and noticable effect on older engines... my 93 Mazda :thumbup:

 

All Civics except the 99-00 Civic Si run just fine on 87 octane. Unless of course you are running forced induction or NOS. If you have high compression or forced induction/NOS then you should use 91 or higher.

 

I can't run 89 with the 10% ethonol in my car or else the CEL comes on. :dunno:
Someone explain that...

 

Lol - it's ok, I'm not at redline or anything. I just let it run higher than usual... move my shift points up a 1000 rpm or so, and don't mind letting the car drive for a while at 4-5K. It heats up MUCH faster than if I just shift through the gears to 5th, and let the rpms settle around 1500 or so, in my "gas saver mode"... takes FOREVER that way. I mistated when I said "really high revs"... let me correct that to "medium revs."

I knew a guy around here with a white Civic EX coupe who would routinely drive around town (smallllll town here) at 7000-ish rpm in first and second gears... he also had a cheap N1 knockoff muffler, just the muffler, so it sounded like the classic "angry swarm of bees" swooping across town. You could hear him from almost literally a mile away if you were in the right place.

Surprisingly, though, his car took all this punishment and came back for more every time - the first time I was really impressed with the D-series engine. He must have done this redline dance around town all last spring, and the car never died or leaked or burned oil or anything... yeah Honda....

 

I run 91 from day 1. Nothing less.

 

Anything higher than 87 is a waste of money.h:

 

from you name I am concluding that you have 99EX, so running high octane is like taking money out of your wallet and throwing it in a garbage can. go read about octanes and what they do and what they are for and you will feel like a dumbass. unless of course your ex is turbo, or running higher compression ratios then stock.

 

haha, the octane theories.."hmmm, if I buy the highest octane gas, then I'd get the highest possible performance for that gas"

WRONG, WRONG, WRONG!!! in simple terms, octane is just a measure of how well the mixture acts during compressed loads. As pressure goes up during the compression part of the motor, temperature increases also. If you have too much pressure caused by a higher-compression motor, the air-fuel mixture reaches above the auto ignition point causing what we know as engine knock (Thermodynamics, Boles and Cengel, page 460).

----Having an EX motor does not need such a high octane. 87 is perfectly fine.


------But I would look more into what additives could help clean off residue on your valves and so forth. I like to use Cheveron cause they make the inside of my engine feel good. At least that's what the commercial says..Plus, they always have cute cars and very nice Bathrooms for me to POOP ON!!!!:thumbup:

 

LOL i use 94... :thumbup:

 

I use mid-grade (89). I used to use the highest I could get, but quite honestly, your car only needs 87, and it ran ****ty.