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Does higher octane fuel really work?

By CheeJun on 18 Nov 2010

Attached Image: f8140fd1ec3eb2e15ac38ce1be13_grande.jpg

This debate has been going on and on for ages. So I decided I should give it a go!

It was not exactly what you would think. There are tons of people who will tell me that its psychological and so on. But this test was different. I had half a tank of regular Shell 95 in my tank left and was driving around normally till it was almost empty. Then my mother went along and filled our Nissan Latio with half a tank of V-Power without my knowledge because she overheard from me that I wanted to give that theory a go that higher octane fuel equals to better car performance.

So I went about driving again the next day and the next feeling that the car was really a little different. Its acceleration became sharper, even though it is a tiny 1.5l, there was a slight difference. I could pick up speed more quickly than before and the whole acceleration process was smoother. However, once I've settled into a cruise, everything felt normal again, till I floored the pedal again to overtake. It is uncanny how this works because the octane level or rating refers to "how much fuel can be compressed before it spontaneously ignites". So the higher the compression ratio of a car, the higher octane required for the engine to perform at its optimum level. And for a car like the Latio, I wouldn't even dare to call it a performance car even though its the 'Sport' version. Its engine 'moos' on acceleration and 0-100 takes forever. So I wonder why even without my knowledge that there was V-Power in the tank, the car did feel slightly more lively to drive than compared with the lower octane fuel.

So if anyone here can explain this 'phenomenon', I would gladly like to read your explanation because its either my mind is playing tricks on me or the car really does benefit from higher octane fuel irregardless of its compression ratio.

shell v-power, petrol woes and 1 more...

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Written by Cheejun
Hi everyone, I’m Chee Jun and cars have always been a passion for me since young and writing about them is one way to express myself in the motoring world.

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ER-3682 Nov 18 2010 07:27 AM
Yes,i also noticed 98 petrol has better fuel economy.
Ruykava Nov 18 2010 11:54 AM
I think it's cuz of the additives,which smoothen the engine, rather than the octane rating itself.
Watwheels Nov 18 2010 11:54 AM
If you do a search online, you can find the answer. The higher octane rating actually "retards" the combustion process or they like to call it "slow burn".
Let's say your car's engine has the typical 10: 1 compression ratio (this means the air/fuel mixture is compressed to 1/10th of its original volume) and uses the recommended 95 RON. And let's say if you use 92 RON you start to experience pre-ignition, meaning before the air/fuel mixture can be compressed to 1/10th of its original volume it became unstable and self ignited making the car jerky and loss of power. Using 95 RON the air/fuel mixture is stable enough to hold itself until the spark is delivered and the mixture burn away fast enough to give out the energy needed to push the piston head down. What 98 RON does is that it burns slower dan 95 RON, it's stable under high compression, does not self ignite, and as it burns slower it burns the air/fuel mixture more uniformly giving out that "slightly more energy feel" that you feel during acceleration and some ppl claim better fuel economy.

To summarise, 92 RON is what I would call most "volatile" when it comes to combustion, this fuel has little or no additives added and it's in its most original state. The higher the RON rating more additives are added to make the petrol less "volatile" and more stable under high compression conditions.
So to me the premium grade fuel is actually "contaminated" with additives and it's not better in anyway as quality is concerned. So now you know the misconception that most ppl have on premium grade petrol.
Cerano Nov 18 2010 12:34 PM
watwheels, ruykava is right, this is due to the additives not so much the RON.

RON only matters when you have FI or High comp NA
Carer Nov 18 2010 05:20 PM
watwheels is right. imagine before the pistons move to the end, there are 'minor combustions' that retard the piston's direction.

with higher RON, the petrol can sustain a higher level of compression before combustion occurs. this is very critical for engines with high compression ratio.
Melvyn Mar 25 2011 12:22 AM
Here's a good read that quite niftily sums up the causality of higher octanne fuel to power. Saves everyone a need to type out long explanations laugh.gif
In fact, do go thru the whole site. It's really quite informative.

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