rolling

iTrader: (2)

heya, I was just curious if I coul duse a lower (87) octaine gas and if it would void warranty, or NOTISIABLY reduse performance, will it do and ACTUAL harm to the system?
or will it adjust accordingly to whats available?

thanx guyzzz

Scott n Houston

Any, modern NA car should run just fine on lower octane. Yes, you'll lose some power, but I doubt it will be that noticable.

If you're doing this to save money, then it would be worth experimenting and seeing if you notice. I doubt you will, but I don't know how hard you drive.

Your engine will retard the timing to prevent detonation that you'll get with lower octane, and this change in the timing will cost you power. The amount will depend on your location, humidity, elevation, etc.

If you try it, you won't void warranty, and you won't hurt anything.

RxZ

When you try the lower octane, just watch for the knocking noise. You will have to get more technical people than me to tell you why, but my understanding is that if the engine knocks every now and then, then no problem. However, if it constantly knocks with the lower octane gas, then that can cause engine troubles in the future. Again, that is my understanding, so hopefully someone else can clarify this. In any case though, even if the knocking is harmless, I wouldn't want my Z making that noise everywhere I went just to save 2-4 bucks per fillup

Scott n Houston

Modern cars all have knock sensors in them to prevent this noise.

Knocking is caused by gas detonating early. Higher octane is more resistant to burning. This resistance allows manufacturers to create more horse power and run higher compression. As the gas is compressed, if it detonates early, you get a knock sound from 'detonation' which is gas burning before it's supposed to.

The knock sensor changes the timing of the firing within the cylinders. This timing change is where he'll get reduced HP, but he won't hurt the car. It's just causing the engine to run less efficiently.


It's a myth that getting higher octane gas can increase HP. That's only true if the engine is designed to handle it. In reality, if one of us put 114 octane in our Z's, there would be good odds it might not start at times because that is very resistant to burning.

Also, there's a myth that higher octane burns easier... that is actually backwards. 87 will burn too easily which is why high performance cars need higher octane.

ssc

iTrader: (1)

i agree, not worth the few bucks you may save...i would just put in the good stuff everytime

Scott n Houston

Read this...
I just did a search and came up with this.
It's about as good an explanation as you can get.

http://www.caranddriver.com/article....&page_number=1

Alonjar

Just a note, in my personal experience with other cars (never tried with a Z), i always made better mileage off premium (well, cars that were designed for premium), to the point that it basically canceled out any price difference.

Really, those few dollars you are saving, are not worth it, if only for the fact that the lower octane will cause extra wear and carbon build up in the engine.

hypeiv

iTrader: (2)

I would be interested to know if you get lower gas mileage with the lower octane. On my old car it recommended 92 octate or better. The book said I could use lower grade but i would get less power. I used 87 for a few weeks but I noticed I had to fill it up sooner. It may have saved me a little money but the lower gas mileage minimized the amount I was saving.

hypeiv

iTrader: (2)

My parents had an old Toyota AE86 that lasted us over 200k miles and we always put the 93 octane in it. They swore the reason the car lasted that long was b/c of the good gas they used and when they replaced this car with a protege that was tuned for 87 they still put in 93 thinking it would help it last longer. Then they noticed that one day the car wouldn't start and when they finally got it going they took it to the dealer the dealer asked if they had been using 93 octane and told them not to use it. Once they put some 87 in the car had no problems starting. They have since only used 87 or 89 on the car and had no problems.

So I agree 114 might cause a car designed for 93 octane to stall.

BigMoeTaki42

Very interesting, thanks for posting this man.

HOMiEZ

iTrader: (1)

if higher octance is more resistant to burn, than why do i get better mileage with lower octane gas? for example, I once got more than 420miles on one tank using regular. But on preimum gas I mostly hit somewhere from 350-400 at most.

JonsilvZ

I tried 87 oct once and started to get knocking noise. I regret it and Ive been using premium since. When you drive a high performance sports car doesnt it deserve the best?

The Brickyard Rat

iTrader: (1)

False savings.

Scott n Houston

Um, the short answer is, "I don't know."

My statement is 100% true about the burning however.

As for your situation, one tank of gas comparison isn't enough data to say whether the gas was the determining variable. You could have had a totally different type of driving, traffic or not, highway more than city... I don't know.

My guess though would be that, lower octane gas causes the engine to retard the timing and the burn. You lose horsepower and I'm guessing that maybe there's less gas being burned on each firing of the spark plugs because of that....
That's a total guess, but it sorta makes sense.

Brandon@Forged

Here's a good link: http://home.pacbell.net/sfnelson/fue...ion__etc_.html

"Can higher octane fuels give me more power?
On modern engines with sophisticated engine management systems, the engine can operate efficiently on fuels of a wider range of octane rating, but there remains an optimum octane for the engine under specific driving conditions. Older cars without such systems are more restricted in their choice of fuel, as the engine can not automatically adjust to accommodate lower octane fuel. Because knock is so destructive, owners of older cars must use fuel that will not knock under the most demanding conditions they encounter, and must continue to use that fuel, even if they only occasionally require the octane.

If you are already using the proper octane fuel, you will not obtain more power from higher octane fuels. The engine will be already operating at optimum settings, and a higher octane should have no effect on the management system. Your driveability and fuel economy will remain the same. The higher octane fuel costs more, so you are just throwing money away. If you are already using a fuel with an octane rating slightly below the optimum, then using a higher octane fuel will cause the engine management system to move to the optimum settings, possibly resulting in both increased power and improved fuel economy. You may be able to change octanes between seasons (reduce octane in winter) to obtain the most cost effective fuel without loss of driveability.

Once you have identified the fuel that keeps the engine at optimum settings, there is no advantage in moving to an even higher octane fuel. The manufacturer's recommendation is conservative, so you may be able to carefully reduce the fuel octane. The penalty for getting it badly wrong, and not realizing that you have, could be expensive engine damage.


Does low octane fuel increase engine wear?
Not if you are meeting the octane requirement of the engine. If you are not meeting the octane requirement, the engine will rapidly suffer major damage due to knock. You must not use fuels that produce sustained audible knock, as engine damage will occur. If the octane is just sufficient, the engine management system will move settings to a less optimal position, and the only major penalty will be increased costs due to poor fuel economy. Whenever possible, engines should be operated at the optimum position for long term reliability. Engine wear is mainly related to design, manufacturing, maintenance and lubrication factors. Once the octane and run-on requirements of the engine are satisfied, increased octane will have no beneficial effect on the engine. Run-on is the tendency of an engine to continue running after the ignition has been switched off, and is discussed in more detail in Section 8.2. The quality of gasoline, and the additive package used, would be more likely to affect the rate of engine wear, rather than the octane rating.

What happens if I use the wrong octane fuel?
If you use a fuel with an octane rating below the requirement of the engine, the management system may move the engine settings into an area of less efficient combustion, resulting in reduced power and reduced fuel economy. You will be losing both money and driveability. If you use a fuel with an octane rating higher than what the engine can use, you are just wasting money by paying for octane that you can not utilize. The additive packages are matched to the engines using the fuel, for example intake valve deposit control additive concentrations may be increased in the premium octane grade. If your vehicle does not have a knock sensor, then using a fuel with an octane rating significantly below the octane requirement of the engine means that the little men with hammers will gleefully pummel your engine to pieces.

You should initially be guided by the vehicle manufacturer's recommendations, however you can experiment, as the variations in vehicle tolerances can mean that Octane Number Requirement for a given vehicle model can range over 6 Octane Numbers. Caution should be used, and remember to compensate if the conditions change, such as carrying more people or driving in different ambient conditions. You can often reduce the octane of the fuel you use in winter because the temperature decrease and possible humidity changes may significantly reduce the octane requirement of the engine.

Use the octane that provides cost effective driveability and performance, using anything more is waste of money, and anything less could result in an unscheduled, expensive visit to your mechanic."

rolling

iTrader: (2)

wow thanx allot you guys all have VERY convincing and informative facts considering the positive/ negative tradeoffs, the one thing that sounds consistent is the "false savings" which makes the most sence to me lower grade = less efficency/ power therefore having to buy more of the lower fuel..

gas in my area is only sold in 87, 89, and 92 some places have the 114 but i dont think so!! i guess ill continue using the 92 for best overal results

thanx for the VERY detailed explanitions !!!

Scott n Houston

Yeah, 114 octane isn't found really at commercial places. They have it at the track though, and I've heard of people going there to get some thinking it will help.

If you have a turbo car, you can benefit quickly from that high octane if you flash the ECU to take advantage of it.

NorCal350

All that I can find is 91 around my location

NismoChic

<slap> no lower grade for you !!!

RBlover69

iTrader: (2)

sorry for being off topic , are you carribean.........only seen the word rawtid from fellow island people