justinc

I have a 91 nissan 240sx should i be using premium or regular gas?

West

Only if you are modded.

justinc

So if i get exhaust ill need to use premium

cheater240

My '91 owner's manual calls for 91 octane (premium).  I put in 89.  I suppose Nissan bumped up the timing a little to get some more power and that required the 91.  

Anyone feel any difference with the 91 octane?

West

Hmmm, I thought the manual said 87. I always run the highest anyways, even when I was stock but it doesn't really matter for most of us. I had a JWT ecu in my old 91 so I had to run 91 no matter what. I run 91 in my Turbo now and it does fine.

You dont really need to start using higher octane gas until you have about 3-5 of the major bolt ons IMHO. Still you can get away with 85 octane.

Only thing I really noticed different when I would switch from low octane to higher octane was less engine knock and honestly the lower octane felt faster sometimes when I wasn't highly moded. Remember the higher the octane the harder the fuel is to ignite.

cheater240

Yes, the harder the fuel is to ignite also means a slower burn.  This means the computer can advance spark.  THIS means (up to a point) more power.  

Does the KA have a knock sensor?  If not, I sure wouldn't run anything under 91.

justinc

Im running regular gas and im stock is that okay or will something happen to my car?

justinc

If i switched to premium does this mean more power ?

West

Nope.

anthony240

just better gas mileage.

drifterx

i feel my car rides like shit when i put in 87 Octane
it only rides bad when i gas hard but if u drive slow it doesnt feel different

justinc

im at a half a tank if i add premium gas will anything happen if i mix the two?

cheater240

There can be power gains from higher octane fuel, IF your car was calibrated to take advantage of that higher octane (read slower burn).

Since the 240SX (at least my '91) calls for 91 octane, I would believe there to be a power loss by switching to a lower octane fuel.  I have felt this loss, and it sounds like others have as well.  Not much, but noticable.

Now, if you put 103 octane race fuel in your Ford Festiva are you going to see any power increase?  NO WAY!  But the 240SX was calibrated to run BEST on 91.  

Running on a lower octane probably doesn't hurt anything because the computer will retard spark timing to compensate for the quicker burning fuel.

justinc

Is it okay to switch between the two?

cheater240

If the car has a knock sensor, it will adjust spark advance to compensate for the lower fuel.  

I wouldn't say its OK to run less octane than what the manual says to run, but everyone (me too when I'm cheap!) does it and the computer strategy will compensate for it

justinc

Dude i always thought i should run regular gas thats what it says in the manual

justinc

If im at half a tank can i put some premium gas in to fill it up?

bison

NO JUSTIN!!! NEVER DO THAT OR YOU WILL SCREW UP YOUR ENGINE BEYOND REPAIR!!!

Just kidding.  Of you course you can fill up with premium even with a half tank of regular.

drifterx

it is ok for 240sx to run the best stuff cuz it is not a domestic car...
the manual said u have to run atleast 89 octane right?
if a chevy ran premium the car would be messed up...
i noticed gas milage increase with better octane and i feel more power but that is me,

drifterx

i forgot
VOTE ME FOR PRESIDENT 2016

96SEChick

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from drifterx on 11:53 pm on July 13, 2001
it is ok for 240sx to run the best stuff cuz it is not a domestic car...</td></tr></table><span id='postcolor'>

Actually, it depends on which domestic car you own. &nbsp;Camaro's and Trans Am's pretty much have to run on premium, or else the engine won't run as smooth and you will get a slight ping. &nbsp;On a Cavalier or a pickup?--87 octane is good enough.

Depending on the gas prices (which look like a seismograph for the past few months), I use 93. &nbsp;91 is kinda hard to find in OK for some reason. &nbsp;

Jeff240sx

Higher octane= better gas milage. &nbsp;KA motors have a knock sensor in them. &nbsp;Less octane=more knocks and pings in your engine. &nbsp;There is a slight power difference using 87 octane since our engines have been advanced from the factory. &nbsp;I KNOW my manual and my gas door says PREMIUM (93 octane) ONLY. &nbsp;I wouldn't run brake fluid where the manual says ENGINE COOLANT ONLY, would you?
-Jeff

justinc

I live in canada and i seen mostly 91 octane

all cars sold in north america must be able to run on 87 in order to be sold here

gt7152b

Not in my part of North America. Several cars sold in the US require 91 octane or more. Higher octane just resists detonation better than lower octane. If you don't have knocking with 87 octane, it will work fine in your car. If you want to run higher octane, you should probably advance your timing to take advantage of it. Some cars have ECU's that will automatically advance timing for higher octane fuel and will back it off via the knock sensor for lower octane fuel. My Chevy Blazer is like this and I switch back and forth between 87 and 93 octane all the time. I can tell the increase in performance with 93. Many cars that run high compression like the LS1 Camaro's/Firebird's and Maxima's require higher octane to prevent detonation from the higher compression. Alot of turbo/blown engines are the same way because the effective compression is raised under boost.

andwys

I use 91, and have noticed a little gain in gas milege but not to much. &nbsp;The car rides smoother and has quicker &quot;go&quot;.
Oh Lauren go to &quot;get-n-go&quot; they have 91 octane and they are friendy from the word go oh oo

geerhedz

cheater is right would you want to put 87 in a vette?.....no. higher octane dosent give everone more power. but a dual overhead cam 4 valve engine with somewhere around 9:1 compression likes 91 or higher. but to tell you the truth i dont like premium these days they dont crack the fuel right on the tower anymore (this is the process for turning crude oil into gas). in fact most outboard engine manufacturers tell you to run 89 cause the premuim is basicly doctored up cheap gas. thet they put a lot of antiknock chemicals in it so what ive been doing lately is running 89 with octane boost and i actually had better results with that. i recommend outlaw products but some premium ive had good luck with exxon, texaco, citgo.

JeffNJ

I know I mention it a lot, but I'm on my second 240 now, so I frequently compare them. &nbsp;I bought both cars used, so I assume each engine was already used to a certain octane? &nbsp;Is that possible?

Anyway, doesn't matter. &nbsp;When it comes to octane, the answer is simple for any car at all. &nbsp;Fill your tank with one like four times or so (to make sure you've flushed all of the other kind out of the lines and the bottom of the tank) and see what it feels like. &nbsp;Then, try it again with a different octane level. &nbsp;I do this every time I buy a car. &nbsp;Every time.

My '88 Jeep Cherokee (I wasn't always a sports car guy) seemed to absolutely demand 93. &nbsp;Anything less seriously reduced it's &quot;pep&quot;. &nbsp;My '91 240 SE honestly seemed to prefer 87. &nbsp;Of course, it never minded the good stuff, but it ran really strong on even the 87, so I just kept buying that. &nbsp;My lastest 240 doesn't seem to care one way or the other. &nbsp;I've run it for a full month each on 87 and 93 and for the life of me, I don't see a #### difference.

That said, just try 'em and use your favorite. &nbsp;I'm convinced octane is just not as important as gas companies want you to believe. &nbsp;Give your car what it seems to want, period. &nbsp;=)

vancouvers14

for some cars, higher octane is strongly recommended, but....
all cars the usa and canada MUST be able to run on 87. &nbsp;it is required

transient

What about the quality of gas itself? As someone pointed out, it's not all the same from station to station... Is there one gas station in particular that most of you go to?