What is the factory recommended octane rating for a 1990 Civic Si?

Will a higher octane benefit a stock motor?

Thanks in advance

 

anybody know? please, I do not want to waste money on 93 octane if it ain't doin me any good

 

From the 1990 Honda Civic Owners manual:
"Use gasoline from pumps labeled unleaded, with a pump octane number of 86 or higher. The pump octane number is an average of the Research (R) octane and Motore (M) octane numbers. Use of a lower octane gasoline can cause persistent, heavy "SPARK KNOCK" (a metalic rapping noise), which can lead to engine damage if severe."

Me, personally - Ever since I've had my 1990 STD hatchback, I've only ever used premium.

 

87..using 91 is just wasting money on a stock motor

 

Stock compression ration = 87,
Me = 97+
stan

 

Thanks a lot guys

 

i run 91 in my B16, but with a 9.5:1 ZC i think its a waste, unless you have severe carbon build up and compression is higher.

 

Well lets look at it this way:
Octane in a measure of how the fuel resists to burning or "pre-detonation". The lower octane you can use without detonation the better. Otherwise you may not be burning it throughly.

So the benefit on the stock motor with more octane would be the ability to run more timing. Get a timing gun and start by advancing your timing 2-4 degrees. You might get more but go up slowly.

To sum it up that is the reason boosted and high compression cars need more octane...because the motor is running hotter and may ignite the fuel too soon. Higher octane will not give you more power, it will allow you to run more boost, compression and or timing. That is where you will get your power.