mb27

I haven't put 87 in the z, but my previous car was a 2000 celica gt-s which according to the manual required 91 octane. By mistake one time I filled the tank with 87 and the car ran much more rough and lost some zip (well, what little zip it had). After that experience I don't really want to try this with my brand new z.

DmitryZ

And that’s also my point!!!! - how do YOU know that it won't hurt your engine? True "Many of the engines in today’s cars are designed to operate effectively on the least expensive gasoline available". But this is not an old 240sx that you can fix with a screwdriver (my beater car). A Z has a high compression engine, which happens to be extremely sophisticated. Thus, it does not fall into "many" category. Just look at how long it is taking to come up with an ECU upgrade for the car.

The articles that you quoted applies to stupid people who think octane rating has something to do with "quality" of gasoline i.e my sister who insists her hyndai needs "good gas".
It has nothing to do with a Z.

My point is: by saving yourself a couple bucks you are taking a gamble. Engine design varies greatly. If you can compensate for knock in one car that doesn’t automatically mean it will work on every car or work well on every car. I am not trying to tell you that you are wrong because I really don’t know for sure. In fact your links and the paragraph you posted above are all true but they DO NOT necessarily apply to our cars.

A good analogy for what you are doing is this – “From now on to save money I will put 3 quarts of oil after every oil change because most engines can handle this type of abuse.” Can that be done? Sure! Will your car still work? Sure! But how would you know that it’s not going to screw up your Z engine long term?

Bottom line:

This forum is for discussing stuff not telling everyone they are fools (a lot of people fail to grasp that concept). You can be right/I can be wrong. I would probably put over 90% of people in this forum (including you and me) into “I know very little about Z engine” category. Hence if you start a post and make a bold statement like “you guys are all fools and wasting your money” you should have something better to back that up than a couple of Internet articles.

Just my .02

Sorry for the long post

DmitryZ

thanks

old_s13

iTrader: (1)

Oscar> It doesnt matter if the car can "run" on 86, that is not the point. You can start a car on carb cleaner and it will "run," does that mean its good? This topic is silly...

For those of you wondering, there have been quite a few incidents of motor failure with the new Celica because people use the wrong gas and the motor gets damaged.

The SOHC KA 240SX motor is designed for 87.. if you want to juice as much power as possible, or if your motor is old (like mine was) and the head was shaved/rebuilt, I actually found that 92 worked better because anything under that would ping -- even with the factory timing setting. Then again, there are a lot of 240SX owners running turbo motors (SR or KA), it would be wise to run QUALITY oil and gas on these motors. Why?

The concept is simple. If your motor is old and crappy, like a SOHC KA motor.. and is designed for 87, then go for it. Check the price on ANY high-performance motor (SR20DET, VG30DET, 350Z VQ) and you'de have to be foolish to NOT fillup with quality fuel. I am even picky as to what gas stations I go to, let alone what grade of gas I buy. Same goes for ANY part that goes on my car, nothing but the best.

Again, WHY own a Z if you are not interested in performance? Posts like this really bother me. Its no wonder Ferrari is so picky about what happens to their parts and vehicles.

Duflacci

Boomer

I use 91 or higher octane in all my cars, most of the manufacturers have recommended it at the least. I used it in a turbo w/8.8:1 CR and in my 97 Accord VTEC Honda recommended to use 87. Why use it on a car with 87 recommended? Because I don't ever want any knock at all in any engine of any car I own, because I don't abuse them, but I drive them hard within their limits. Detonation is death for an engine driven that way. What if you get an 87 octane that has been diluted down by water or some other crap in a service station's tanks? Believe me, the extra octane is a safety margin for my engines. I would use 93 or 94 in my Z if I could find it where I live and I really don't care if I wasted a $100 a year either. Getting by on a high performance engine's like the Z's is like playing Russian Roulette. Will it blow up the engine if I run it to redline today using 87 octane?

Your advice is both ridiculous and uninformed and I am wondering why you would buy a new Z and take such chances. Probably because you don't own a Z at all and would like one or more of us to abuse our cars by taking your pathetic advice. I call this a troll, a liar and a sick puppy,someone who gains pleasure from others' misery.

Subbacultcha

man this topic has gone from one extreme to the other. That government article was written specifically for you!!! You putting higher than required octane gas in those engines is a waste of money! It truely does not offer any "safety margin"! Just like how a car using a lower than recommended octane will run inefficiently, a car using a HIGHER THAN RECOMMENDED OCTANE WILL RUN INEFFICIENTLY TOO! Your car will emit extra pollution because this.

jeez, just enter "high octane" in google and you will find many articles explaining this.

Im sorry but:
boomer = pot
and
oscarmeyer00 = kettle.

Buub

iTrader: (1)

Sorry but I don't feel confident in taking your promise to my dealer when I need warranty repair for my engine because 87 octane gas DID **** it up. Will you cover the bill?

Nissan says you must put 91+ octane gas in the Z. They say so for a reason. They designed the car, shouldn't they know?

Once again, try and get this through your thick skull: that article was written for mom and pop who drive Tauruses. It was not written for high-performance cars that are driven hard. We are not in the "most" category that you are referring to. We are the exception, not the rule.

You should really stop using your Dad's computer at night. Did he give you permission? Or do you sneak on the computers at your junior high school to stir up trouble? At least your grammar and diction aren't terrible, that's a good start.

samw1978

I won't put a lower octane gas in the car than what the manual suggests... I want my car at its best performance at all times
Moreover... putting a lower octane gas will save money, as you said, $100 an year, that I don't care much since you could afford the car already
I understand your point though, if I were driving a tercel today, 87 is more than enough for the car, and I won't get a much better performance from a higher octane gas. But you have a 350Z, not a tercel, due to the high compression ratio, 87 is not enough for the engine, anywayz, just put whatever the owner's manual suggests IMO

SteveZzz

Oscar-

One of the things that you're overlooking is the cost of reduced performance. You might think you're saving 100 bucks a year, but I'd bet your spending more. Here's why.........

Let's assume you only spend $1000 per year for gas. If the average price you pay per gallon is $1.50 and you average 20 miles per gallon, you're going to drive about 13,300 miles per year.

There's no doubt that the lower octane fuel will offer some sort of reduced perfomance. Forget the fact that you aren't pushing your car to 130+, or trying to be the quickest off the line. The one place that the reduced performance WILL show up regardless of your driving patterns is in reduced overall FUEL MILEAGE!!

So, if you're saving $100 of that annual fuel budget of $1000, you're saving 10% on fuel cost. A 10% reduction in gas mileage will take you from 20 MPG to 18 MPG. I know that in reality the equation isn't this linear, but you'll certainly get less MPG. Even if it's only 2 or 3%, you'll end up buying more low octane fuel to compensate. So you're probably saving very little. Bottom line........ the premium fuel costs you almost nothing when you factor in the fuel mileage difference. Not to mention all of the other possible negative effects.

And by the way, you're using the article you linked to as your reference to why you don't need higher octane. In fact, you even quote it in your post to help you make your point. But I noticed you conveniently missed the last sentence of the first paragraph. ..... Hmmmm. my owner's manual says to use premium fuel!!

BigBadBuford

I would use the grade of gas recommended by the owner's manual. In almost every car I've owned I've noticed that doing this gives you the best combination of performance and fuel economy. My '86 GTI called for regular gas, and with regular gas it would get about 32-33 mpg, but you could feel the knock sensor kick in from time to time on hot days, so I put in 93 octane for a while. My milage dropped to a steady 28 mpg.
I tried the same in my 240SX. It had the KA24DE which called for 91 octane. I used 93 Octane (the closest I can get to 91) and I got around 24 mpg. I decided to try 87 octane for a few tanks and my mileage dropped to 22 mpg although I didn't notice any detonation. However, the price in gas was offset by the gas mileage I was now getting.
The only time you want to use gas other than what the owner's manual recommends is when you are using a car with a built engine, an old car designed for leaded gas, or a car w/ out a knock sensor when you are getting detonation. Especially on cars designed for leaded fuels you want to use a higher octane than what is called for by the factory because the lead effectively raised the octane rating of the gas.

Giedrius

Some good reading about octane and how it's calculated, etc.

http://www.seansa4page.com/resource/octane.html

insaneamine

iTrader: (1)

I am a firm supporter of higher octane in performance vehicles.

As many of you know, I used to be a chemist, I worked in a top tier refinery for three years where all we did was fuel; gasoline, diesel, jet fuel, kerosene, etc. Part of my job was a rotation in the “Octane Lab” where the different grades of gasoline were tested.

I used to smuggle out 113 octane reference fuel by the quart to put into my MR2 Turbo which had a 12 gallon tank. A couple of quarts would certainly raise my octane from 93 to about 97 or 98. The difference was like night and day. That little puppy screamed! Consequently though, I burnt through my Turbo/Exhaust manifold gasket twice. I put over 140k miles on that car.

Let me tell you one thing… you may THINK you are buying higher octane but it isn’t always true. Sure there are laws regulating such things but consider this…

Pop Quiz:

You got some union monkey plant worker named “French Fry” blending 93 octane that day. You are testing a final for shipment, the tanker is waiting, your best second and third determination proves the stuff is only 91.5. What do you do???

a. Bump the tank down to 89 and keep the tanker waiting.
b. Re-blend the tank and try to get the octane up and keep the tanker waiting
c. Use the old pencil method and under pressure from your supervisor “tweak” the results and let it go.

Take a guess at what happens more often than not. Also take a guess why I don’t work at that dump anymore and why I will never buy products from this major refiner.

P.S. Don’t ask which company it was, please.

I got the following from: http://www.howstuffworks.com/question90.htm

What does octane mean?

The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.

The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.

The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.

It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.

During WWI, it was discovered that you can add a chemical called tetraethyl lead to gasoline and significantly improve its octane rating. Cheaper grades of gasoline could be made usable by adding this chemical. This led to the widespread use of "ethyl" or "leaded" gasoline. Unfortunately, the side effects of adding lead to gasoline are:

Lead clogs a catalytic converter and renders it inoperable within minutes.
The Earth became covered in a thin layer of lead, and lead is toxic to many living things (including humans).
When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more. Airplanes are still allowed to use leaded gasoline, and octane ratings of 115 are commonly used in super-high-performance piston airplane engines (jet engines burn kerosene, by the way).

I2h8BMW

Not worth it. Since mfg. suggested 91 or higher, I go with 91. We don't get higher octane here in CA.

DmitryZ

I wish people would find a more mature way to express their opinions.

You should read Boomers post more carefully. He said diluted gas i.e. in reality some crappy gas stations do some nasty things. The pump might say 87 but if it is diluted with some kind of crap, so the station can make more money, you are putting something that has a significantly lower octane rating in your car. Hence if I absolutely need gas and have to buy it at some place that does not look that respectable I will tend to get higher-octane gas. Example, I used to always put 87 in my old 240 until one day I filled up my car and it knocked all the way back to my house. Why? Because I got lower than 87 octane gas at a place that did not look too respectable. Nowadays, I never wait for empty and fill up when its halfway at places that I trust.

Dmitry

P.S. I hope we are not having a case of troll multiplication here

old_s13

iTrader: (1)

I would use 92 if it was a Taurus... S-H-O

Hey man, thats a damn good Yamaha motor!!!

old_s13

iTrader: (1)

Hey Dmitry, what year is your S13? Now that you have the Z, maybe now is a good time to build up that old_s13!

- Mike

Subbacultcha

Well i reread it and I still get a different impression than you did. I think he implies his car needs higher octane because "he drives them hard" and the gas dilution point is just an afterthought. Besides, there are a billion gas stations around, its not hard to avoid the places that "don't look respectable...."

Buub

iTrader: (1)

Yeah and then Ford ruined it when they decided to use their own crappy motor instead. :-)

raymanZ

Insaneamines writeup is wonderfully stated. As an organic chemist myself, I was just about to post many of the points he brought up.

On a tangent:
I am well aware that knock, which leads to timing retardation, is the major factor in avoiding lower octane gas in high compression engines. But here's a little thought to ponder, which I think applies to low performance vehicles (typical four cyl that only needs 87 octane):

If you have a low compression, low performance beater and dont drive your car very hard, than getting a higher than recommended gas (93 as oppossed top a recommended 87) can actually reduce horsepower since the ignition timing in the ECU is programmed to ignite the spark plugs in a timing that assumes 87 octane. Since 93 takes longer to fully burn, the effectiveness of the higher octane gas is reduced since you want most of your gas to burn very early in the expansion stage of the cylinder movement (less volume, more pressure, more torque). With the higher octane gas and and ECU that is programmed for 87 octane timing, this wont happen.

Now of course, this ignores the issue of knock altogether which is why it is not a "real world" scenario. I readily acknowledge that in most cars, knocking (specifically with 87 octane) will usually be (if not always) the overriding factor to consider in engine performance. Remember, knock (spontaneous combustion) depends on both compression AND temperature. So thats why I will always use 93 in my Z, but for my older 1994 4 cylinder altima that has lower compression, mostly used for short trips, and driven mildly (limited heat buildup), I dont think the advantages of 93 octane are THAT great.

But 87 octane in a 10:1 compression high performance engine? Not too smart if you ask me.

I want to conclude by commenting further on Insaneamine's statement of lead based additives to improve octane. Many of the octane boosters you now find at auto stores, although not lead based anymore, are actually still metal-based (MMT: (methyl cyclopentandienyl manganese tricarbonyl). I'll tell ya, the manganese is not going out your exhaust, so I look at the use of MMT is still with a lot of skepticism. It may not harm your cats or engine, but as a chemist, I don't like the idea of adding non-volatile metals(manganese) to an engine. The best way (I feel) to boost your octane a few points is through the use of different organic (and combustable) solvents such as toluene or xylene. These have higher boiling and flash points than many of your linear hydrocarbons contained in gas (heptane and lower). You would essentially be doing what the gas companies do anyway in formulating gas with a certain octane rating by the correct mixing organics with the varying degrees of boiling and flash points) I work in a lab so toluene is dirt cheap. amazing how much certain auto stores sell a small can for though!


RaymanZ