john0213

hum...i know u guys will blame me not using the search again, but wait before u do that, i've searched it and saw only 2 threads(wtf!?i 've seen many post talking bout this before, where did all go? ), anyways, i want more info.

ok, now as more people are getting their cars, i wanna rediscuss on this topic, which is what type of gas should we use? furthermore, i got another question(y do i have so many question!? ), if the car requirs u to use 91 gas and instead u use 87 gas, what are the effects and will there be any major damage if i wanna keep the car for long term? I'm saying the effect/damage on spark plug, and cylinder itself, etc. And can anyone explain to me thoroughly in a mechanic view?

yeah i know i got a lot of question cuz i'm getting the Z soon and so is my dad, he's getting the 2003 LX 470 in Octocber and we both need some advices on gas and stuff, u know, we wanna keep our car for long, so we don't wanna mess around 87 gas if it causes damage~(i don't wanna see my engine getting problems and i got like this-------> )

rai

well sports compact car did a test with 91 octaine (you can find a link from yesterday). They said that 91 the engine was close to the knock sensor. I believe that is is advaisable to put 93 octaine. 87 will not give you the power and also may contain less detergent. The engine should be protected by the knock sensor, but will have less power.

the price difference is about $2-3 dollars(US) a tank that is like $50 to $100 a year. You may find the price different in your area, but I don't think it's worth it to save a few bucks. I don't think any damage would occur, but why take a chance?

Besides let your dad fill er up, he can afford it.

zzzyaaa

Most gas stations have 91, not 93. Is there a particular brand that has 93?

bhobson333

Please check this thread - I'm convinced. I will probably try to use only Amoco Ultimate.

https://my350z.com/forum/showthread.php?threadid=2634

padam07

Within the last few months or year (I am not sure) Sport Compact Car ran an article about the grade of gas in California. They were talking about how the highest standard grade of fuel would change from 93 or 92 to 91. For the rest of the country it is mainly 93. They had a pretty good write up talking about the change because they are based in California and they deal with a lot of crazy boosted and high horspower vehicles and lower octane fuel causes detonation early which cause severe damage to the engine.

zzzyaaa

Thanks 07, now I can keep my eyes on the road instead of looking for 93.

Touring6MT_Z

John,

If you want in depth information written by expert about this topic, the best way to get the info. is search the Internet. I use Google, typed in 3 key words "gasoline octane rating", I got tons of links. So you can do the same in a few seconds. You will get your answer written by expert in the field.

Here are some short answers for you, written by non-expert. In the nutshell, the Z is tuned for 91 octane. If you use lower octane rating, the knock sensor will detect the detonation and retard the timing to compensate for it. The accelleration will suffer, so does the gas mileage. I experimented with 87 octane on my '95 Maxima, that what I got. You can do the same with a tank of 87 octane regular after break-in and judge it for yourself if it worth the saving.

tbcz

Must be a regional thing...95% of the gas stations I've seen aroung Philly (including most of Jersey) have 93 as their premium. Of course, then Sunoco has 94. There are a few stations (Hess is the first one that comes to my mind) that use 92 for their top grade.

john0213

i'm asking about the gas thingy cuz it's not just $2-3 dollars difference in a jeep, it's gonna be hell lot more. and as i've said, i'm going to keep the car for long so is my dad ,therefore i need some more advices bout the gas thingy.

another question is related to the maintence cause, will the cheaper gas affects the engine so the maintence cause will be more expensive? if yes then i'm sure it's not worth it to use 87.

bhobson333

Here's my best advice on this subject: Follow the manufacturer's recommendation and put in the 91 octane through the break-in period and then for a while after, so you can get used to what your car is supposed to be; a baseline, if you understand.

Then buy a tank or two of 87 octane.

My guess is, you won't buy the second tank of 87, you'll understand what they meant by "91 recommended" and that will be the end of the story. But you really should try it just to ease your mind. (Maybe buy a half-tank! )

Keep in mind, I'm not some octane snob. I currently drive a V6 Accord that recommends 87 and that's what I put in. I have tried higher octane and get no benefit from it because my engine is designed and tuned for 87. The Z engine is designed and tuned for 91. 'Nuff said.

mdouvris

The Amoco Ultimate is the only fuel for this ride. It costs more because it is better. period

Enforcer

BLUF: Use the high octane.

Timing and knock already covered. Amoco already covered. Detergents already covered. I did some research on this years ago. My memory wanes, but will try. As I recall, the difference is how quickly the air/fuel mixture burns and where/when it burns. Ideally you want the mixture to burn (explode) at precisely the right time in the cylinder when the valves are closed. The terms "flame-front" and "vapor-pressure" come to mind.

The way I remember it, a low octane fuel with lower compression burns slower than a higher octane with higher compression. I think of it this way, if you pass your finger through a candle flame quickly, you won't get burned. If you hover your finger over the flame it will burn your finger. It also can burn in a different shape. Sort of like focusing or diffusing the flame. Compression plays a big part.

Not what you asked about but helps to understand...A lower compression engine can not crack the higher octane fuel as efficiently as a higher compression engine so you end up with more unburned fuel even though your running high octane. IE little performance increase. But does not hurt engine components, seem to remember something about the catalytic converter having to work harder.

To your question...burning lower octane fuel in a higher compression engine results in it not burning as quickly as the higher octane fuel would. Translate this to mean more heat transfer than the engine was designed for, not just in terms of quantity but also where and when. Detonation, ping, etc. With today's computer controlled valve and timing engines, this gets a little more complicated. And with the new electronic spark control systems, thoughts of punch through come to mind. Enter the knock sensor, used to retard engine timing to lesson detonation. But the way it works, you have to have detonation first then the timing gets retarded. Better to not have the detonation in the first place. You will have detonation even with the higher octane fuel, just not as often (understatement) with the fuel the engine was designed to run on and at the timing the engine and the computer control was designed to run with.

You can notice this by a "pinging" or "knocking" noise. That noise is not a good noise, it means engine life is being shortened. It is a warning to you that you have a tank of bad gas, better take action immediately. Note the knock sensor and anti-knock control merely lesson knock, it does not prevent, it's just there to minimize the effects and severity of detonation. Comes from the mixture burning at the wrong place/time. In the push rod days, you could end up with burned valves, bent rods, blown gaskets, overheating, etc. A little different now with overhead cams. I don't know for sure but it can't be good. Basically the engine is experiencing internal forces in places and directions and times it wasn't designed for. Some guesses would be burned valves, timing chain stress, cam/follower wear, guides and seals failures, and premature failure of the part that enables the variable timing in this engine (don't know what it is called).

Other factors include build-up of nasty black gooey stuff (LOL don't remember the name) on engine components that can further reduce the engines efficiency and heat dissipation capabilities (translate this as engine life).

I have been running high octane in all my vehicles, two require 90 and one requires 89. But I run 92 or higher. Have never had a problem and never hear the pings with high octane. But put in $5.00 of 87 once (was desparate one late night and the one station opened had their 92 pump out of order) and oh boy...ping city. The next day filled up with high octane, no pings.

So, when in doubt, go higher not lower. And if your desparate one late night, don't fill up, just enough to get you home.


Enforcer

john0213

thx for the info man~!!! yeah and about the amoco ultimate thingy, i don't know what the hell that is cuz I'M A CANADIAN EH!~ yeah whatever, i'm asking the gas question cuz i wanna make sure if the 87 gas will do any harm or damage to the engine, especially my dad's new LX470, u know, it's gonna drink the gas like us drinking coca cola man~ but as i read along i don't think i will screwed around with the regular cuz it might cause some problems. and also enforcer, ur's so informative ur info is gonna shut my mouth for awhile and i'm definitly gonna tell my dad about the explanation man~! some nice write up!!