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Old 30th June 2007, 03:57   #46
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High octane fuels are used in performance cars because they dont want the fuel air mixture to ignite before full compression cycle. Normal econo sedans need 87 octane because the compression ratio is not high. If you put high octane fuel in cars that need only regular fuel, you will not have a clean combustion and FE goes down.

High octane doesn't automatically mean good FE and long engine life. In fact it may do more harm than good if not recommended by company.
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Old 30th June 2007, 06:13   #47
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I had this question niggling me for quite sometime now and I stumbled upon an answer to this on the American Automotive Association website:

AAA News For You - Gas Watcher's Guide

AAA - Maintaining & Repairing Your Car

From whats been said, it is pretty much evident that premium fuels do not contribute to better performance of a car and can rather deplete the performance of the car unless they are recommended by the manufacturer. Also, recently I read somewhere that less than 2% of the cars on American roads require premium fuel. If this is the American scene, what can we say about India ? So IMHO, I presume we would do better by sticking to the manufacturer's recommened fuel as mentioned in the owner's manual rather than experiment and burn our fingers later.
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Old 30th June 2007, 07:03   #48
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The premium v/s regular fuel debate will go on and on and no one will be able to provide clear cut answers. Till then, I'm just enjoying the show....
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Old 30th June 2007, 07:55   #49
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I have been using these premium fuels in my 2yr old santro erlx since day 1. Was using hp speed for a yr and then a year back changed to shell premium. Recently drove down to Hesserghatta resort "our own village" and only got normal IOC fuel. However experienced no difference as such.
BTW here is the link to hyundai site recommending premium fuels
Hyundai Motor India - Official Site of Hyundai Car Products
well they don't "recommend" just say "its a good idea" - very cleverly keeping themselves safe
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Old 30th June 2007, 10:56   #50
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Quote:
Originally Posted by carfreak View Post
the last time i gave my palio for service at rf motors,the authorised tata-fiat dealer,they advised against using premium fuels.i casually told the mechanic i used only speed,and he told me fiat does not recommend using 91-octane fuel for the palio,but to stick to the regular fuel.he said it could result in fuel pump damage!!

strangely,autocar india used speed petrol in their long-term palio 1.6 and they said the performance and FE improved after the shift to 91-octane.according to them,high compression engines run better with higher octane fuel.

anyway i switched back to the regular fuel now!!
The Fiat workshop warned me against using premiums or fuel with additives, reason cylinder heads likely to accumulate some white deposits. Fiat recommended only 87 RON. I believe it is not the Octane number, rather the additive causing problems. My petra used to run better on Shell Super/ IOC Premium, I switched back to IBP Regular.

Another observation, some numbers in pollution check seem to have gotten higher while using premium fuels.
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Old 30th June 2007, 11:32   #51
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Quote:
Originally Posted by theMAG View Post
Speed, during the time of its 1st release was known to seize a few engines -
Mag, problem started with fuel pumps. Pumps started packing up.

I've been using IOC Premium 91 for Optra from day 1. Once a month I add IFTEX while filling. Have not faced any issue. Also I fill only from our office designated pump.
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Old 30th June 2007, 11:38   #52
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Default Premium Fuels

I wonder why the fuel companies, unlike other manufacturers of various goods, do not list the names and quantity of additive they add to make it a premium fuel?

Isn't this mandatory by law as is for other products?
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Old 30th June 2007, 11:47   #53
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I have been using speed/premium unleaded at Shell for a while now in my Baleno. However, last week, when I was close to empty and went to tank up at Shell, they were out of stock with premium.. and got the car filled with regular unleaded.

I have found the drive to be far more comfortable now. Yes, I do feel a minor power loss, but, my gear changes (unless done carefully) earlier used to have a lot of jhatkas.. now, all that has smoothened out and I find myself using the clutch a whole lot lesser. Quite happy with this experience.. Maybe, I'll just stick with normal unleaded fuel for some time to see how things go.. in anycase, my mileage was only a tad lesser than 12 kmpl.. How much worse can it get with normal fuel!
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Old 30th June 2007, 11:48   #54
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You can get such information through 'Right to Information' Act. These companies are obliged to provide it.
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Old 30th June 2007, 11:52   #55
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That's exactly my point. Why RTI for this mundane information? Isn't this mandatory?

Quote:
Originally Posted by swathyd View Post
You can get such information through 'Right to Information' Act. These companies are obliged to provide it.
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Old 30th June 2007, 11:56   #56
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Gosh, after reading this thread, I am more confused than before. I bought a Fiesta 1.6 in March, 2007. On the advice of the sales guy, I was using ordinary IOC unleaded fuel.
But when I read the manual, I saw that it recommended 91 ocatane fuel, and my inquiries on this website revealed that ordinary fuel was 87 octane. So I started using 91 octane fuel (IOC Extra Premium) for the past month and half--the engine sounds smoother now, but not much difference in FE.
Now I think I will alternate between both fuels , as I don't know which is better.
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Old 30th June 2007, 12:14   #57
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And after reading about premium fuels i wish to share something. When i first checked my F.E it was 12.3 (mixed) x tra premium was in tanks. Then filled normal ioc F.e was 13.6, then ioc normal( full tank) F.e went to 14.3. Then used ioc x tra premium for sometime, didnt check mileage. But the vehicle was feeling heavy and sluggish.


After 2nd service. Filled reliance petrol (full tank) got mileage of over 16 kms. Now again filled reliance petrol and did approx 300 kms( had to fill x tra premium in between) got a mileage of over 15.3 under hilly terrain. t

After filling reliance i was able to feel much better response, previously i had to downshift to overtake. The difference definitely is not psycological. Really unleashing of few more horses.

Onething i took note is that x tra premium is sluggish and so less responsive. After reading opinion by bhpians i seriously consider using normal fuel or reliance whenever it is possible.
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Old 30th June 2007, 12:16   #58
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When I asked Toyota tech guys they said Toyota engines are tuned to work on any octane fuel (normal or premium) although recommanded is 91 octance and above for Toyota Petrol cars. Only Shell provide 91 octane in Normal petrol and all other Normal Petrol we get in India is 87 octane. He told me its my choice to use type of petrol although he recomands normal petrol because engine will work fine even on lesser octance Petrol (87 octance in case of normal) and although recomanded is 91 octance or more.

Few the engines from other manufacturer tend to give jerks/knocks create problem when we use higher octane. What he means is for example If they recomand octane 88 as petrol and If we use 93 octane engine which don't handle this will tend to give problem in long run and sometimes its not noticeable.

He also told me If car give knock/jerks change fuel bunk immediately and most of the times it will be alright without any fixing after 2 or 3 fuel fills.

This kock/jerk issue is very very less with new engines, so using high octance premium fuel is good for new engines.

The old engines (he means engines manufactured before 2003 I guess ) its better we use normal fuel.

Most of the issues mainly because of bad fuel and not becuse of octane we use.

Regards,

Ravi.
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Old 30th June 2007, 12:21   #59
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Quote:
Originally Posted by vnabhi View Post
Gosh, after reading this thread, I am more confused than before. I bought a Fiesta 1.6 in March, 2007. On the advice of the sales guy, I was using ordinary IOC unleaded fuel.
But when I read the manual, I saw that it recommended 91 ocatane fuel, and my inquiries on this website revealed that ordinary fuel was 87 octane. So I started using 91 octane fuel (IOC Extra Premium) for the past month and half--the engine sounds smoother now, but not much difference in FE.
Now I think I will alternate between both fuels , as I don't know which is better.
Our 1.6 manual also recommends using 91 octane. But it is not the octane doing the damage but fuel addictives used to achieve that rating. There is smoothness and silence felt when using IOC x tra premium, but i think IOC normal is also smoother. But speed is not that smooth, niether is power. So dont get fooled by initial smothness, if possible try reliance or shell. And post your feedback after filling reliance. It has done wonders( almost) in my car.
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Old 30th June 2007, 12:28   #60
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Quote:
Originally Posted by ravibhat View Post
When I asked Toyota tech guys they said Toyota engines are tuned to work on any octane fuel (normal or premium) although recommanded is 91 octance and above for Toyota Petrol cars. Only Shell provide 91 octane in Normal petrol and all other Normal Petrol we get in India is 87 octane. He told me its my choice to use type of petrol although he recomands normal petrol because engine will work fine even on lesser octance Petrol (87 octance in case of normal) and although recomanded is 91 octance or more.

Few the engines from other manufacturer tend to give jerks/knocks create problem when we use higher octane. What he means is for example If they recomand octane 88 as petrol and If we use 93 octane engine which don't handle this will tend to give problem in long run and sometimes its not noticeable.

He also told me If car give knock/jerks change fuel bunk immediately and most of the times it will be alright without any fixing after 2 or 3 fuel fills.

This kock/jerk issue is very very less with new engines, so using high octance premium fuel is good for new engines.

The old engines (he means engines manufactured before 2003 I guess ) its better we use normal fuel.

Most of the issues mainly because of bad fuel and not becuse of octane we use.

Regards,

Ravi.
It is not the octane which causes problems but addictives used to achive that octane rating. Are you sure that shell doesnt use any addictives to achieve 91 rating for its normal petrol. We should ask some govt agency to conduct a probe into this ( i know it is virtually impossible) or should find someother means like RTI act to obtain precise info on this.

I dont thing these people will reveal anything without such stern steps from consumers, though they are legally obliged to do so.
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