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Discussion Starter #1
Currently I use Mobil but my company is now switching over to Caltex which means I'll suffer a drop in RON from 98 to 95.

Can anyone tell me (in simple terms) if this will have an effect on the engine? Will I notice any difference in performance or fuel economy (not that I really care about economy, just seemed to be a responsible question)
 

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From the manual.

Use unleaded premium gasoline with an octane
rating of at least 91 AKI (Anti-Knock Index)
number (Research octane number 96). ie RON96

So more than likely could get away with RON 95 however not recommended. Would need to watch for any signs of knocking.
 

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I get my 98oct from Shell of Mobil. I don't trust the other brands.
 

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Perthy, from time to time (probably two or three times in the last year and a half) I have had to use the Caltex.

To my non decerning driving I noticed very little difference. I can't comment on the fuel consumption as it is something that has never concerned me. You cant drive "performance" vehicles (cars or bikes) and worry about that shite.

As always

H
 

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Discussion Starter #6
Thanks guys. In relation to "knocking" what exactly is this. Does it lioterally make a knocking sound??
 

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Yeah exactly. There will be a knocking noise and you will feel the motor "labour".

For the record I normally use Mobil Synergy 8000 which is now, in Newcastle, about $1.20 per litre!

As always

H
 

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Originally posted by Perth 350z@Oct 21 2004, 04:11 PM
Thanks guys. In relation to "knocking" what exactly is this. Does it lioterally make a knocking sound??

This question comes up very few months on most car forums.

Knocking (also known as detonation) is when the fuel detonates in an uncontrolled manner. Instead of following the burn in the way the engine would like it, it ignites in a more random fashion.

Because of this, it puts stress on the internals that they weren't designed to take, and after a while stuff breaks.

You can get knocking when the fuel quality is too low (and the fuel ignites because of the amount of compression you're running, rather than from the spark) or if its too high, and your engine cannot ignite the fuel properly.

Not the best explanation in the world, but its why high-performance motors have to run 95 or 98 RON fuel or risk engine damage, and also why really old, low-tech motors can be damaged by running this "good quality" petrol.
 

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Oh, and for the record I only run BP Ultimate (except when I went down to watch Targa Tasmania, where they only have 95RON fuel).
 

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You generaly get pinging before any detonation occures.

It sounds like shacking marbles in a tin can, It's audible from the driver seat...u can't miss it.

I've had it in my Zed with crap fuel from Shell. Yep, got a bad batch of 98 oct... had to mix it with fuel from another station to fix the problem. I could have got an octane booster but that depends largely on where you are starting from.
 

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Originally posted by scathing+Oct 21 2004, 06:07 PM-->
<!--QuoteBegin-Perth 350z
@Oct 21 2004, 04:11 PM
Thanks guys. In relation to "knocking" what exactly is this. Does it lioterally make a knocking sound??

This question comes up very few months on most car forums.

Knocking (also known as detonation) is when the fuel detonates in an uncontrolled manner. Instead of following the burn in the way the engine would like it, it ignites in a more random fashion.

Because of this, it puts stress on the internals that they weren't designed to take, and after a while stuff breaks.

You can get knocking when the fuel quality is too low (and the fuel ignites because of the amount of compression you're running, rather than from the spark) or if its too high, and your engine cannot ignite the fuel properly.

Not the best explanation in the world, but its why high-performance motors have to run 95 or 98 RON fuel or risk engine damage, and also why really old, low-tech motors can be damaged by running this "good quality" petrol.


Another important factor which determines the difference between pinging and knocking is when the abnormal ignition takes place. One is before the spark plug fires and the other is after the spark plug fires.

Note below excert.

Detonation (Knocking)
Detonation is the spontaneous combustion of the end-gas (remaining fuel/air mixture) in the chamber. It always occurs after normal combustion is initiated by the spark plug. The initial combustion at the spark plug is followed by a normal combustion burn. For some reason, likely heat and pressure, the end gas in the chamber spontaneously combusts.

Pre-ignition (Pinging)
Pre-ignition is defined as the ignition of the mixture prior to the spark plug firing. Anytime something causes the mixture in the chamber to ignite prior to the spark plug event it is classified as pre-ignition. The two are completely different and abnormal phenomenon.
 

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I took delivery of my Z in May 03 and my manual states that I should use a minimum 95RON fuel. I have always used Shell Optimax with no problems and once I put $15 of Mobil fuel (95RON) when I was out of gas. With this fuel, I did not get hard on the gas and did not notice and problems.
However, I recall DavidM state previously that his manual recommends 98RON fuel as a minimum, but his car is newer than mine.
I am wondering if the later model Aussie Z's have the ECU tuned for 98RON fuel from the factory.
Can you all look at your manuals next time and let me know whether yours states 95 or 98 RON fuel and also state when you took delivery of your Z please.
 

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I use Optimax, I had a bad expirience with BP Ultimate
 

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Mine says 95RON, but as I said I've only ever run the car with that kind of fuel for a week.

As for Optimax vs Ultimate, its pretty line ball. I've had people who have had bad experiences with Optimax as well. To be honest I've never had an issue with either, but people I trust about cars have and so I stick with their opinion.

This post on Silvia NSW might be of interest. I don't know the poster well enough to know if he's full of **** or not, but he says he spoke directly with BP.

As an aside, with the new BP Ultimate advertising blitz, they've also changed the formula etc for the petrol so its not the same "Ultimate" that it used to be.....
 

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It is my understanding that Mobil are the only ones who refine their own premium unleaded. All the other guys blend, so I suppose there is more chance of something going wronf with the other brands??

I have ever only had one bad experience with bad fuel and that was with shell. I put it in my bike one time and it totally farked it up and I was at amaroo at the time.

Obviously the best thing is to find a good petrol station you trust and stick with them.

As always

H
 

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I've owned the car for about a year now......

I agree with what Harry said, though. Some petrol stations seem dodgier than others. I honestly wouldn't put it past them to mix their 98RON fuel with 95RON stuff (or even 91) to improve their margins, since I have had the occasional "bad batch" which isn't brand-specific.
 

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KY350

Purchased my Z August 2004 (havn't checked the exact build date but can do so). The owner's manual states:-

"For Europe and Australia use unleaded premium gasoline of at least 98 octane (RON)"

It then continues:-

"If premium gasoline is not available, unleaded regular gasoline with an octane rating of 91 (RON) or above may be temporarily used, but only under the following precautions:-
- Have the fuel tank filled only partially with unleaded regular gasoline and fill up with unleaded premium gasoline asap
- Avoid full throttle driving and abrupt acceleration"

cheers
coatsie
 

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Thanks Coastie - my manual reads the same as yours except mine says 95 where yours says 98.

Now i'm wondering if the ECU is tuned for the different fuels and if so will there be a big differnce? I think in Japan, their premium fuel is 101 RON, so I'm guessing that the factory would not bother tuning the ECU to 98 RON if their regular unleaded is 95 and premium is 101.
 

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I use Opti-Expensive and always from the same servo. Is that anal or what ?

I have heard that Caltex is the best burning fuel but the RON rating is lower than BP,Shell, and Mobil.

I have tried all 3 each with 2 tanks and a reset of my ECU each time I changed brand in my WRX and always went back to Shell.
 
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