Expensive petrol and what octane you use
 

What octane you guys use for you 8?

I hope bros here will post cheap petrol offers when they see it.

What i realise today is that Shell is offering up to 15% discount and SPC's max is 11%.

Not going racing, so use the cheapest that the car can handle. Octane 95

Just need to find out. I was drive in a Rental car Mazda 6 overseas. and when I was about to top up the petrol, theres a sticker stating Min 95 Octane, (which is the same as our Rx8 car)

But I fill the mazda 6 with 91 Octane , and drove the car. I do not find any power reduction between 95 Octane and the 91 Octane.

But why is it that Mazda put the sticker there stating that the car can only handle a MIN 95 OCTANE?

Any ones knows why????

I wonder why too. The petrol in Australia is mainly 89 octane and premium is at 92 Octane. So how can the 8 handle it? So i was wondering whether our 8s here can take 92 too?

Anyone try the 92 Octane.???

Would it damage the Engine?

If it would not damage the engine and the only disadvantage is losing power , then I may be considering switching to 92 to save money.

Hi all - small hijack :D

What's the octane for V-Power?

most of the octane in sing r 98,v-power is so-called 98+...caltex ever gt 100,dun noe if still hv.tis hv been discussn b4,the # is juz a guide s 'hw gd the grade' of the fuel against 'detonation',the higher the lesser the risk.

V power - 98 octane with more additives

Caltex - 100 octane phased out long ago...

After buying an RX-8, I always wonder why are we so concerned over saving some money on fuel? This is not an economical car to begin with... and the amount lost on depreciation is much more.

Nup - all the big brands are 91 for unleaded, 95 for Premium Unleaded and 98 for the major brands equivalent of Shell's Optimax (eg BP's Ultimate and Caltex Vortex).. 89 was the old standard (leaded) fuel octane rating..

Octane is also known as the "knocking" index. It is a measurement of how cleanly the fuel combust. If the fuel cannot combust smoothly, it would cause knocking(combustion that would be slightly off the timing and that in turns can cause stress to the engine parts due to unexpected movement). The engines have tolerance for some knocking and is stated in the manual. If you use a lower than recommended octane you will lose some power(due to the fact that the fuel did not combust cleanly at ignition).

To exaggerate the point, we use very simple illustration. Imagine a piston engine(I know the 8 is a rotary but a piston is easier to illustrate in this case) that has piston going up and down. Up after ignition and fully up during the exhause and down after intake and fully down during the compression stroke. This is no brainer. Compressed air/fuel is ignited and explodes and the force drives up the piston. The the piston goes back to compression again after drawing new fuel/air mixture. But imagine the ignition did not cause all the fuel to ignite at once but only some fuel. There would be ongoing combustion even during the exhause and when the piston is getting ready for the compression stroke, the air is still expanding due to the "late combustion" of the remaining fuel. Thus you would have opposing forces and that would cause energy to be lost and thus you experience power loss.

The car can take some amount of such abuse and thus it will be rated...minimum how what octane you are suppose to use. It should have some tolerance. If you use slightly lower that the level the engine is designed for, you lose some power without significantly harming the engine. But if you use an octane too low(maybe diesel?) and your engine would knock horribly and spoils. The question now is how low is too low. That really depends on how much tolerance the manufacturer gives. But note that your engine could really suffer in the long run if you use something beyond its tolerance.

I doubt i saw wrongly. Maybe its just different in melbourne where i lived for a while. I remembered it was 89 and 92 because it struck me that the octane was so low as compared to Singapore when i first went to melbourne 2 years ago. And i realise alot of vehicles were of lower compression there than in singapore because my sis bought a rav4 there and i noticed the compression is lower and later on they phased out 2 litre rav4s and replaced it with 2.3 litre ones; maybe because of the lower compression the 2 litre rav4 is not powerful enough.

Of course optimax is available in shell stations and i reckon its the highest octane you can get in melbourne.

And bros in singapore. SPC actually is giving a max discount of 17% as compared to shell's 15%. SPC posted 5% discount + SPC card but they actually add another 6% when you pay.

There could be a different standard that could confuse. Singapore uses the RON. Some places uses the actual anti-knock index which is the average of RON and MON. Typically, the MON is lower than MON. So what you see as 92 may works out to be perhaps equivalent of a 95 or even 98 RON.

By the way, higher octane doesn't really outperform the lower octane. Higher octane simply means more additives such as aromatics and highly branched alkanes which are anti-knocks agents that has low energy density. Moreover, higher octane doesn't prevents deposit from forming as well.

But low octane can cause knocking(aka pings/pre-ignitions etc etc) and persistent knockings can damage your mechanical parts of your engine.

With the sky high fuel price, did any one here ever tried the 92 octane petrol? I wonder if it can be used as in the states, they use mainly 89 octane petrol.

US using MON values... so it's lower... 89 MON is about 95 RON (but some have said 89 MON is about 98 RON... but that I'm not too sure)

MON = Motor Octane Rating
RON = Research Octane Rating

Waaa liew....

http://www.shell.com/home/Framework?...ange_0830.html

bro, since u oredi got the 8, i shld tink spending the few xtra dollars shldnt be a prob.... rite? go for a minimum of 95 octane.... nvr 92..... in spore context, that is....

We can't use 92... JDM models not tuned. Even if you broquet it.

Can anyone confirm the octane of Petronas max? Is it at least 95?