Which Octane to use??

[Crab Walker]

Ok so how can I find out if 9.5:1 compression is low enough for 87 octane. Or should I get 89 or 94?

I know that low octane gas on a high compression motor causeing knocking but what does high octane gas do on a low compression motor???

also, My brother drives a honda with a prelude motor in it that has a 10.0:1 compression. He uses 94 but i dont think he should.

[nrcooled]

I found that the KA felt more responsive with the lower 87 octane. With my SR I run nothing but 93 octane though.

[kazuo]

For S13 SR20DET motor I wouldn't run anything less than 91...

S14 SR20DET I wouldnt go less than 94.

Remember our octane ratings differ from the Japanese...

[Pearl Sharkie]

go here http://greennature.com/article347.html

I hope this will help

[nightwalker]

The only thing that I notice is that with 87 or 89, I run out of gas sooner. With 91, it stays in the tank longer. This is due to the fact that 91 burns slower. It kind of equals out for me anyways. I use 91. But I may switch to 89, because I'm getting a slight gas smell from my car. Not having a cat doesn't help either.

[PANDA]

i've personally found 87 to be the best performing for a stock KA..both in my 240 and previously in my 93 Altima...

[Flybert]

Nissan told me that higher octane gives my KA better performance. It's written on the car.

[mastaflash05]

alot of this stuff is not true.

the only reason you need higher octane is to reduce the chance of detonation. if your motor will run on 87 without detonating then it is fine to use that fuel. using a higher octain will not give you more power, but it will allow you to make more power safely. If you run 94 octane gasoline in a car that will run fine on 87, then you are wasting your money. this is a common misunderstanding.

if you are running higher boost or compression then you do need to increase the octain of the fuel you run, only because of the risk of detonation.

[phrozen]

also it dosent matter where you buy gas from, shell, am pm, chevron, arco, ect..

i know someone that distributes gas to those companys listed above and said that they all recieve their gas from the same place and the same grade, and fill up to truck tankers.

only place that has better gas is 76, and he said it is worth the extra few cents.

i dont believe there is a big big difference between 87-91 octane gas, 91 does feel a bit smoother and might last a bit longer(might just be figments of our imagination) but unless you drive a shitload every week why not give your car what it deserves =). too bad we dont get like 97 like europe

[kazuo]

alot of this stuff is not true.

the only reason you need higher octane is to reduce the chance of detonation.

Exactly.

Higher octane isnt gonna make the car faster... but it will reduce the chance of detonation, and detonation = bad

91 on Redtops, 94 on S14 Blacktops.

:D

[misnomer]

Uh, do you have an SR? I didn't see it mentioned in the thread :P If you do, then I would stick with higher octane (91+). A KA shouln't matter too much, unless you are knocking you can run on 87, it's what I use :P Higher octane gas isn't necesserily slower burning, but it takes more heat to get it going, hence why it can deal with higher compression. "Octane" rating in gasoline is simply a rating of it's resistance to knocking. It has nothing to do with performance or mileage. Basically, everything I've read says to buy the lowest octane rating for your car (unless you are pinging or knocking). So, 87 it is!! Also, keep in mind altitude, way the hell up here, I can run lower octanes than I could at sea level. Air pressure will effectively add to the compression in the engine.

[PANDA]

Exactly.

Higher octane isnt gonna make the car faster... but it will reduce the chance of detonation, and detonation = bad

91 on Redtops, 94 on S14 Blacktops.

:D

and just where do we go about finding 94 in California?..lol..

[Flybert]

and just where do we go about finding 94 in California?..lol..

There are some 76's that sell race gas in some places. I think I heard there is one in Pasadena.

[PANDA]

i can only imagine the cost of that...lol..

[kazuo]

and just where do we go about finding 94 in California?..lol..

There's a gas station, like, a block away from Sears Point that sells 100... there is also another station in South San Jose that sells 100. Both straight from the pump.

Or you can buy it in a can from like auto supply stores.

Just mix the 100 with 91 and off you go. :D

That's what Keith does for his S14 Black... no issues yet.

I wouldn't want to run 91 on a S14/15 motor..

[Doriftomodachi]

there is a 76 in long beach that sells it for around $6/gallon

[PANDA]

for a daily driver...shiiiieeet...lol

[Modern Angel]

also, My brother drives a honda with a prelude motor in it that has a 10.0:1 compression. He uses 94 but i dont think he should.

I used to drive a 97 Prelude with the H22a4 engine in it. It requires 91 octane or higher. Even the FSM says this. So your brother is right.

:)

[sykikchimp]

The 240sx Manual says that you should use 91 octance for best performance. This means the ECU is tuned for that to receive max performance. (I think the 89-90 models suggest 89 octane.)

and engine knock is caused by the pre-ignition of fuel as it's compressed in the cylinder, milliseconds before the normal spark plug fires.

If you use a lower octane rating, the engine will slightly knock, and the ecu will detect it, and retard your timing. The car will run fine this way, but you wil not receive the best performance.

Also, some fuel companies don't put the same additives in the lower grade fuels. Texaco only puts their special additives (like Texaco's "Clean System 3") in their mid-grade, and high-grade fuels, but not the low grade 87. My parents ran a Citgo, and a Texaco. Citgo does run their additives in the low grade.

Just another thing to think about.

[AKADriver]

The 240sx Manual says that you should use 91 octance for best performance. This means the ECU is tuned for that to receive max performance. (I think the 89-90 models suggest 89 octane.)

My 1990's manual suggests 87.

The higher-compression early '89 models might be different, but cars built from 2/89 to 7/90 should use 87.

[thx247]

No problems running 91 so far, until I get a chance to test for knock I'll probably keep using 91 on the stock motor anyway. For daily driving I imagine 87 would work just fine, but since I dont really drive lightly I've just stuck with 91. Probably a waste of money but oh well =(

[sykikchimp]

not a waste of money.. it's called "peace of mind"

It's the same reason I run oil that cost $6 a quart.

[mastaflash05]

not a waste of money.. it's called "peace of mind"

It's the same reason I run oil that cost $6 a quart.


theres absolutly nothign wrong with using higher grade fuel. its like spending the extra money for mobil 1 vs. any other synthetic.

[suhster85]

where can I find 94 gas in southern california? and what will happen if I use 91 on an S14 blacktop? Will there really be that much of a difference on the engine? Performance wise or anything else? How unsafe is it to use the 91 on an S14? I'm just wondering because I got a nice price for an S14 blacktop swap and
1. I have never seen 94 octane in southern california.
2. dunno how much it costs.
3 dunno if its gonna be worth it to go through the extra hassle of finding 94 octane all the time and maybe just get an s13 engine since I'm going to mod it anyway.
Any people with S14 blacktops in southern california have any input on this?

[AlligatorBling]

The sticker on the inside of my gas cap cover says premium isnt such a bad idea.... but then again momma always said dont believe everything you read...
::shrugs:: ...

[s0ldats]

after always running 91 (highest around my area), i decided to fill up with a tank of 87 and note the differences (mileage etc). right now, i can feel that it's not revving as smoothly as the 91 octane. who knows, maybe it's just in my head.

[rewplayff]

is there a difference between the s14's ka. can i use lower octane, or will my car explode. 91 in my area is around $1.89-1.95. it would be nice to save a couple cents here and there

[Ghettokracker71]

on the gas door of my '91 FB it has a sticker that says "for maximum performance use premium grade gasoline." ...thats what I've ran in it since the first time I filled it up :)

[thx247]

Hey now! Synthetic motor oil is a different kettle of fish!


I love my mobil 1. So clean after 5k its crazy

[Jeff240sx]

Use Premium Fuel Only

Why would you argue with it? $.20 cents a gallon = $3.40 difference on a full 17 gallon fillup. Case closed, just like this thread.
-Jeff