[RX135]

Originally Posted by iceman91

if you dont mind me asking what are the other reasons???
thanks..taken the signature off my friend in malaysia who drives a nissan..thats his nickname/his car's

Not a problem, Sire!

I do not use it for following reasons:

1. It is not readily available and quite far from the city. I do not travel that much (I wish I could).
2. Even if I can manage to fill it occasionally, it is not a good idea to mix Petrols of different octane ratings.
3. The more I searched for information on high octane fuels, the more I am convinced that they do not do any value addition to your MPFI car. Strange but true! I had posted whatever I found in some other thread. I was religiously using Speed 93 earlier, but now got back to regular 87 Octane unleaded. Unless I find compelling reasons to use higher octane fuel, I'll keep on using same.

[Jaggu]

one thing i have found, high octane=more money=less indian customer=less adulteration=happy car :P

[Rtech]

t is not a good idea to mix Petrols of different octane ratings.

What makes you say this?

[RX135]

Originally Posted by Rtech

What makes you say this?

That is what I could gather for various posts. Can not authoritatively justify this, but let me explain my understanding.

Higher octane burns slower than lower octane fuel, which reduces chances of "knocking" at higher RPM and higher compression ratios. Mainly in performance cars. Now, if you are mixing higher octane and lower octane fuel, there is no guarantee that knocking will not occur. (I assume, same density for both fuels here, which means mixture of fuels will enter combustion chamber.) Thus defeating the purpose of using high octane fuel.

[simran]

Originally Posted by RX135

which means mixture of fuels will enter combustion chamber.) Thus defeating the purpose of using high octane fuel.

The mixture would have a higher octane rating than the lowest octane fuel, so the probability of knocking will come down. Also, subsequently, your octane rating would tend to be equal to the octane you are filling up regularly.

Simran

[amitoj]

Originally Posted by Jaggu

one thing i have found, high octane=more money=less indian customer=less adulteration=happy car :P

lol.. thats interesting... but is the following possible:
high octane = more money = less indian customer = low sale volume = more adulteration to make up for low volumes = one very very sad car?

[xstream_nos]

does Speed 93 really carry 93 octane...???? n have ya guys tried addin Toluene (sulphar free) to have an increase in the octane level.... this idea was posted earlier by Dominic (Shreyas).
i tried it... it did give sum promisin results...

[RX135]

Originally Posted by simran

The mixture would have a higher octane rating than the lowest octane fuel, so the probability of knocking will come down. Also, subsequently, your octane rating would tend to be equal to the octane you are filling up regularly.

No my dear friend. Probability will not go down. Can you say that throwing a cigarette butt in a petrol tank is less dangerous than a burning matchstick? All you need is a self igniting spark to cause knocking. Even small quantity of lower octane should be able to produce that.

Agree with second point, but then I can not fill it up that often with Reliance 98 Octane petrol.

Last point, I am still trying to understand usefulness of high octane fuel in MPFI cars. Help if you have any information in favour of it.

[DCEite]

Originally Posted by amitverma

this is a nice topic.
i personelly use Indian Oil's Xtra Premium 91 Octane...
btw does any west delhi guy know the best petrol stations around?

In south Delhi, the three petrol pumps lined up(ioc,Hp,bp) near Hyatt regency flyover (ring road bikhaji kama palace).. all three are ok, but i prefer the HP one.

No info about west delhi though.

[Rtech]

Can I mix different octane fuel grades?

Yes, however attempts to blend in your fuel tank should be carefully
planned. You should not allow the tank to become empty, and then add 50% of
lower octane, followed by 50% of higher octane. The fuels may not completely
mix immediately, especially if there is a density difference. You may get a
slug of low octane that causes severe knock. You should refill when your
tank is half full. In general the octane response will be linear for most
hydrocarbon and oxygenated fuels eg 50:50 of 87 and 91 will give 89.

Attempts to mix leaded high octane to unleaded high octane to obtain higher
octane are useless for most commercial gasolines. The lead response of the
unleaded fuel does not overcome the dilution effect, thus 50:50 of 96 leaded
and 91 unleaded will give 94. Some blends of oxygenated fuels with ordinary
gasoline can result in undesirable increases in volatility due to volatile
azeotropes, and some oxygenates can have negative lead responses. The octane
requirement of some engines is determined by the need to avoid run-on, not
to avoid knock.

This and a whole lot more useful info on fuel can be found
Here

[RX135]

Originally Posted by Rtech

[
This and a whole lot more useful info on fuel can be found
Here

Very good article. Excellent resource on Fuels.

[simran]

Originally Posted by RX135

No my dear friend. Probability will not go down.


Last point, I am still trying to understand usefulness of high octane fuel in MPFI cars. Help if you have any information in favour of it.

I stand corrected on the first point, after reading the last few posts.

And I read someplace on this forum that compression ratio * 10 should be roughly the fuel octane number you should use for your car. Therefore, if my car's compression ratio is 9.5, upto 95 octane is Ok, but anything beyond that will not prevent knocking (article also mentions some figures in a table, but those are for cars using carburettor). Coming back to the article link which was posted, it says that the downside of using low octane fuel is engine repair, while that of using a high octane fuel is 'throwing' away money. I feel since the high octane fuels come with additives, it may be better to go in for them (less hassle of buying and putting additives). Also, since a movement within 6 octanes is said to be Ok, going upto Speed 93 should be Ok since conventional fuel is 87.

Lets see the cost differential for a year assuming car runs 10000 kms and gives an avg of 15:

Normal (Rs 43 pl) 28667
premium (Rs 44 pl) 29333

diff is Rs. 666/- for one year.

Methinks instead of adding additives, one should find a reliable pump, and start with 91 octane, see performance, increase octane and keep doing this till you get consistent good performance and then stick to that fuel.

S

[iceman91]

most indian cars except the ford mondeo are in the ratio 9:1 or close to that so 91 octane should be good.

i have personally used and race on dom's mixture and it is GOOD...but about daily use i cannot say much...oe things for sure just takin a whiff of toulene gives you a BLOODY STRONG kick in the head...

[Shan2nu]

Well from my experiences all i can say is that my car seems to prefer normal BP fuel to Speed (not speed 93). Filled speed last week as we had to go to Mangalore, car started pinging and felt very unhealthy. On the way back, filled normal fuel and all was fine. But, Xtra Premium from IOC has given me the best performance so far.

I really don't trust speed. IOC 91 over anything, anyday!!

Shan2nu

[gamerno1]

i hope i dont go off topic but can someone tell me which is the best fuel for a 99 zen (carb) ?