Is high test really necessary?
 

Does anyone use 87 octane fuel on a regular basis? I tried one tank and didn't notice any knocking or any other ill effects but I hesitate do use it regularly. Any thoughts would be appreciated

Sorry bud, I've only ever used the recommended 93 octane.

Nope, never considered it. When I bought the car I knew it required premium and that's what I put in there. Why would you consider putting less than what the manufacturer requires in the vehicle? I mean is $4-$6 a tank going to make that big of a difference in your wallet?

On that note, the motor is engineered (compression, timing, and all that) to use that specific test. You may get away with a few tanks, but eventually you'll get that bad luck where it causes misfires or failed detonations and start causing major issues.

You do realize there's a reason they tell you to use premium, right? It's not a conspiracy between Nissan and Big Oil. The car will knock on cheap gas until it dials back enough timing to run safely. Knocking is never good, and pulling all that timing out loses power.

I looked up the price difference where you live. At $0.40 a gallon difference, if you were empty, that's $8.00.

One good denotation could cost you a whole lot more! Didn't you know the car needed premium before you bought it?

You quoted my post so I'll respond that premium is $.30 higher here. Not sure what your looking at, some stations may be that high but QT and Costco aren't.








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If you use 87 over 91, the loss of power will be X amount, meaning it will take (the same, if not more than) X amount of power to get your car up to speed.

The price difference vs the HP loss difference makes 91 almost the exact same value


This is only for cars tuned for 91

Nobody that I know of. I got in a bind and put just enough low octane in the tank to get me to a station with ethyl.

You may not have heard anything but, if you were pushing the engine very hard, it was there. The ECU can adjust to minimize knock but that decreases power. Try your test on a hot Summer day and you may be able to hear the knock.

Edit: To answer the question in your title: Yes. 89-91 octane is required for proper operation.

The engine is tuned from the factory to run on an octane (AKI) of 91 or higher.

I'll spare you the details on octane needs, (which you should do some research on), but the short version is, octane represents the ability of the fuel to avoid knock (explained bellow).

Having said that I'll mention three important issues to keep in mind at the pump.

1. A combustion engine produces torque (and by extension, power) without destroying itself rapidly in the process through a series of carefully TIMED combustion events -- that's what the ignition timing tune controls.

2. Combustion events that are NOT properly timed are what we call commonly call "knock" (auto-ignition or pre-ignition of fuel), and knock can cause severe engine damage in short order.

3. Three factors contribute greatly to the likelihood of engine knock: (1) Increases in heat in the combustion chamber, (2) High levels of compression (either based on design of piston of through forced induction), and (3) increased engine load (primarily by way of corresponding increases in heat and pressure within the cylinder chamber in the production of peak torque).

You live in FL and drive a high revving, high output sports car with fairly high compression pistons.

Does going below the recommended octane sound like a good idea, keeping these three points in mind, the nature of your engine and the environment in which it will operate?

If you think about all that and conclude, "Yes", then best of luck to you...

AKI < 91 is not recommended.

i thought this was a DUI question...

you should've bought a ecobox.

Do not use 87 octane. Also do not use diesel.

:icon18:

My Z runs like a striped ape when I use JP8. :happydance:

:icon18:

Not unless your Z is a 500ZX.

Nobody say this yet. The motor has 11 to 1 compression ratio. That's high for a street motor. Also the combustion chamber design in the head has alot to do with it too.

Has less to do with it than you might think. The car just isn't designed to accommodate for low octane. There are plenty of 11:1 cars that run 87 just fine.

The 370z just like the 350z are designed with a part called a knock sensor. The whole purpose of this part is to detect knock if it occurs and then will compensate by adding more fuel to the chamber to prevent further knock from happening. Knock can occur due to the fuel not having enough octane. Running 87 octane will decrease your hp but that is all it will do.

Nissan 370Z Knock Sensor - Nissan OEM Engine Mechanical

What does a knock sensor do? - Yahoo Answers

The motor has to be knocking before it can be detected and the motor pulls back timing. Knocking is bad. Also, the car can only add so much fuel to compensate.

I know. ;) Just brought that out if the OP didn't know. Alot more goes in to it. Timing, valve lift, valve duration, valve overlap, A/F, etc. ;)

just use the right fuel or sell the car and get the right car for 87

:bowrofl::bowrofl::bowrofl: :gtfo2: it can't run on JP8




try jp4

I think it's interesting how in some parts of the country 91 is the highest you have. We have 93 readily availible and some of the cheap stations run 92.

To be fair, at higher altitudes, like over 7k feet, 89 octane is likely plenty.

If I can't afford premium gas, I don't buy a car that takes premium gas......

This thread...

http://www.gifsforum.com/images/gif/...a7baf3-337.gif


http://i3.asn.im/Meme-suicide-_t147.gif

Engine go boom just like this thread.

^^LOL @ XiP

My Z runs on eggnog. No knocking or pinging here. I do add rum for a nice boost though.

I'm still stuck on trying to figure out the title of the thread. :icon14:

Right?

I thought it was a body building thread at first and :wtf2:

I thought it was a drug test in general.

"High-Test" is an old-school term for premium gasoline. I say old-school meaning the 1950's...

Ahhhh.

Back before records were kept and everything. I see.

:stirthepot: :icon17:

Some cars (like the Fusion with EcoBoost) can run on either, but as it states in the fine print, "the horsepower stated is only achieved with Premium fuel."

The engine is also designed to use both, but to get the performance, Premium should be used.

Wow, we haven't had one of these threads in a long time.

Mods must still be on Thanksgiving holiday sincve the thread hasn't been locked! :roflpuke2:

Simple answer - this was a dumb-arse question! You bought a car that requires premium. If you wanna play, you gotta pay.

Take the number of miles you drive annually, divide by your average MPG, then multiply by the price difeerential between regular and premium. You probably spend more a year on soft drinks or video games.

I mentioned it :)

Yes, and no. Higher compression piston heads tend to be more likely to have flame kernels dissipate irregularly, creating hot spots that may lead to knock by way of pre-ignition of the next combustion event.

This is one of the reasons that it is generally easier to tune a boosted car with more boost but lower compression pistons, rather than just assuming more pressure however its achieved is better. You still have to deal with knock and that's generally easier on a low CR high boost motor, at least using port injectors (in theory you can do more with less using direct injection).

In either case, the ignition advance tables were tuned based on the presence of 91 AKI, so to run optimally and safely, especially under load, going below the recommended octane is potentially risky.

Sort of. It will aggressively retard ignition timing and may also pump more fuel to control what is determined (correctly or incorrectly) to be knock -- HOWEVER, this state of affairs is far from ideal in terms of performance or fuel economy, and will not necessarily preserve the engine.

It's not really simply a secondary map, where you just make less power, as it almost certainly is for an engine where the manufacturer only "recommends" higher octane fuels, but claims it will neither damage the engine nor void the warranty if you use a lower octane -- if nothing else, assume that they don't want to have to keep replacing motors for customers, so they have some confidence the "low octane" spark maps are perfectly fine for normal driving.


Well, true, provided you are high enough that pressure levels are sufficiently lower in the cylinder -- but without a way to monitor what the motor is doing, it is still probably a bit of a crap shoot...

And... if something does break, evidence of the use of a lower than required octane may void the warranty...

Well I didn't think I was that old...kids these days...:rolleyes:

OK got it
 

Thanks to all for the response. High test for now on