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Old 16th February 2005, 21:01   #1
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Default How does high octane fuel improve performance?

Till recently, i was very hesitant to use high octane fuels like Xtrapremeium, Power, Speed 93 etc. But one of my friend regularly fills up one of these in his car and according to him his Mileage has improved by about 1-2 km/l and his car picks up better too.
I have three following questions for which i am very curious about.

1. Do high octane fuels like xtra, power, speed add to FE and Pickup or Both.?

2. Are all of the above types are 93 octane?. (specifically, is Power from club HP 93 octane?)

3. What if i mix and match all the three, because in city traffic its very difficult to stick to just one Brand. That is, if i have 5 litres of XtraPremium on my car, can i top it up with Speed 93?
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Old 16th February 2005, 21:09   #2
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Power is the regular 87 octane fuel from HP with additives,Speed93 is 93 octane fuelwith additives from BPCL and Xtrapremium is 91 octane fuel witha dditives from IOC.
i n addition to these u have the Speed97 which is 97octane with same additives as speed 93.

in mumbai ,reliance also sells its 93 and 98 octane fuels ,but these are without additives.


regarding the technical aspect ,all i can say is that higher octane fuel burns completely and aids combustion.do not know more about it.will leave it to ustaads like Dom,iceman and almost everyone.



i feel u should avoid mixing diifernt fuels .why?????dont ask me.hehe
cheers,

satya
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Old 16th February 2005, 21:24   #3
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Well, generally speaking, high octane fuel has the ability to sustain high levels compression and heat before they ignite.

If you use 87 oct fuel in an engine with a comp ratio of 12:1, what's gonna happen is that by the time the compression levels reach around 9:1, the fuel will self ignite even before the the spark plugs fire. Why? bcoz 87 oct fuel cannot withstand pressure and heat generated beyond a certain compression ratio. This is called premature ignition or engine knocking.

Now for the big question!! Does high octane fuel improve performance? As long as your car doesn't knock on 87 octane, using higher octane wont improve performance.

But sometimes, what happens is that on cars with knock sensors, the onboard computer detects preignition and changes the ignition timing of the engine depending on the fuel, in this case, even thought you might not hear any knocking, the engine is having to sacrifice it's normal functioning to match the low quality fuel.

I usually fill fuel with a slightly higher octane rating than the company recomended rating (just to be on the safer side). I'm pretty happy with 91 oct in my car and didn't find any improvement when i filled 93 oct, be it performance or fuel efficiency.

Shan2nu

Last edited by Shan2nu : 16th February 2005 at 21:52.
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Old 16th February 2005, 21:55   #4
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Quote:
3. What if i mix and match all the three, because in city traffic its very difficult to stick to just one Brand. That is, if i have 5 litres of XtraPremium on my car, can i top it up with Speed 93?
Xtra premium is 91 oct, so don't mix that with Speed 93.

There shouldn't be any difference between 2 fuels with the same RON rating. So, if speed 93 and reliance 93 are both RON ratings, you can mix them.

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Old 16th February 2005, 21:58   #5
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shan ,
what if u mix fuels with diif octane numbers.what will the problem be.i.e what if u mix 98 with normal POWER and what if u mix POWER with normal fuel
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Old 16th February 2005, 22:04   #6
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Quote:
shan ,
what if u mix fuels with diif octane numbers.what will the problem be.i.e what if u mix 98 with normal POWER and what if u mix POWER with normal fuel
You'll get diff octane ratings, depending on how much quantity of each fuel is used. Performance and FE wise, there wont be any diff.

There's nothing wrong in having diff fuels in the same tank (as long as all their RON ratings are equal to or more than the recomended rating).

If your car runs on 87 oct, no matter what combination of fuel you have in your tank, the overall octane rating will always be equal to or above that, since we don't get fuel below 87 oct (in India).

Shan2nu

Last edited by Shan2nu : 16th February 2005 at 22:06.
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Old 18th February 2005, 10:28   #7
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Quote:
Originally Posted by Shan2nu
Well, generally speaking, high octane fuel has the ability to sustain high levels compression and heat before they ignite.
Well said, I would add : If the car has higher compression ratio then use higher octane fuel. Eg; Getz has a compression ratio of 10:1 and I believe 97 Octane will give a boost to its fuel efficiency. Maruti 800 works best with 87 Octane fuel and no point in putting (and wasting money ) higher octane fuel in it.

Now Euro III norms will also give us better quality fuel (30 paise extra per litre) and should increase the fuel efficiency as it will be burnt better in the engine.

Btw: Overdrive in their Getz test drive said that it has higher compression ratio compared with accent is because of the hyundai's confidence in quality of fuel available here. So I guess they meant, Getz should work well with bad quality fuel
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Old 18th February 2005, 11:51   #8
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As far as FE is concerned, just comparing kmpl will not give you a complete picture wrt whether u r saving money or not when switching to a higher octane fuel. What you should look at is rupees per km to compare different fuels.
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Old 18th February 2005, 12:04   #9
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i found this article on the net. It's very informative and to the point.

The Octane Myth

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Old 23rd February 2005, 18:49   #10
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Post Octane Myths

Hey folks, did some R & D on net for Octane ratings and its usefulness for a car. Almost all are unanimous in saying that Fuel with higher Octane rating than recommended for car does NOT give any benefit.

1. No performance boost.
2. No FE increase.
3. In fact, it puts extra load on emission system.

They are relevant for carburated engines which could not efficiently mix air/fuel, and hence causing knocking. For MPFI cars, they are of no use.

Bottomline, use higher octane only if recommended by manufacturer or, if you have used any performance chip requiring higher octane fuel.

Last edited by RX135 : 23rd February 2005 at 19:07.
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Old 23rd February 2005, 18:58   #11
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MODS can we have an FAQ on this ??
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Old 18th September 2005, 22:58   #12
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there is no use for higher fuels for mpfi vehicles in any form, i suggest use only manufacturer recommended fuel
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Old 19th September 2005, 09:06   #13
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Question --- What is the right Octance rating for an Esteem?
I use Speed. Would like to know your opnion on this.

Experience --
Milage ---
I have driven the Esteem with the normal fuel available at BPCL
I did notice that a 10 L fuel getting exhausted in 1 1/2 weeks time.
When I used Speed the same amount of fuel came for 2 weeks

This has been a regular run, where I take the car to work and back. No additional runs. Nothing

Performance --
With Speed, I noticed a good power surge on the low end torque (Meaning car running on the lower 2 gears)
High end Torque, I could nt notice much of a difference between the two fuel types

Your views or comments would be appreciated as it would throw light on the technology and validate my experience too
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Old 19th September 2005, 11:29   #14
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Hi guys I have a 98 zen and i just started putting speed97 and i felt a slight increase in pick up of the car. But my milage did not incerase , i still get the same as i used to before with speed!
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Old 19th September 2005, 11:37   #15
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Quote:
Originally Posted by RX135
Hey folks, did some R & D on net for Octane ratings and its usefulness for a car. Almost all are unanimous in saying that Fuel with higher Octane rating than recommended for car does NOT give any benefit.

1. No performance boost.
2. No FE increase.
3. In fact, it puts extra load on emission system.

They are relevant for carburated engines which could not efficiently mix air/fuel, and hence causing knocking. For MPFI cars, they are of no use.

Bottomline, use higher octane only if recommended by manufacturer or, if you have used any performance chip requiring higher octane fuel.
Hi All,

Mine car (indigo gsx) follow euro-III norms & dealers advise me to got for speed,power & expra Pre petrol only. Mostly i have used HP power only. As rx135 says being an MPFI car wont matter between normal or power petrol. What we need to do ?

Recently overdrive tested all petrol for bikes & said HP power is the best in performance & mielage in terms of money spent. As cars are very much different to bikes ? but in any sense ....Does it apply to cars ?
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