[meerkat]

Originally Posted by RX135

a) On highways, you are driver faster effectively heating up tyres more than in city. If you have less pressure, you might blow up.
b) Ride will be affected in city, but on highways, road is better quality so it doesn't matter much.

Umm... if the tyres heat up more, shouldn't higher initial pressure cause more problem ?
Higher temp ==> higher pressure, so lesser original pressure should actually help !
(This, of course, is complicated by the higher rolling resistance at lower pressure, so the
actual conclusion is not so simple).

Also, if highway roads are better (smoother), there will be less friction, thus
compensating somewhat wrt temperature increase !

[SLK]

Originally Posted by meerkat

Higher temp ==> higher pressure, so lesser original pressure should actually help !
(This, of course, is complicated by the higher rolling resistance at lower pressure, so the actual conclusion is not so simple).

See post 57 in this very topic... might help.

and Wow we are discussing about "Best Fuel"

[meerkat]

Apologies first, for posting off-topic, -- I'm guilty as much as anyone else doing
the same. But my post is relevant to what is being discussed under this thread ...

Originally Posted by SLK

Think about friction caused by air circulation inside the tyre.
Take funny example.... you fill tyre with sand.... the tyre inflates fully, though there is more scope to put in sand to tighten it.
When you drive with lose sand ... its lose particles cause friction and HEAT.
Same happens with air though at faster rotation speeds.
So more Air less fristion between air modecules.
........

Now about Higher pressure....
.......
but friction inside (air circulation) ........ would be less so less heat.

This analogy between solid and gas sounds rather inane. How closely packed
do you think the air molecules are at the higher pressures in question ?
As close as tightly packed sand particles ? If anything, more air molecules
(i.e. at higher pressures) would give rise to much higher probability of
collisions between themselves, not less ! Anyway, how do such collisions
cause temperature rise significant enough towards tyre blowout ?
Do you have any good references in this regard ?
Aren't things like rolling resistance much more important ?

[SLK]

Originally Posted by meerkat

If anything, more air molecules
(i.e. at higher pressures) would give rise to much higher probability of
collisions between themselves, not less !

what can I say!... how big can be a collision in a tight parking lot?... compared to an open highway.

Originally Posted by meerkat

Aren't things like rolling resistance much more important ?

You mean the rolling resistance of the air inside the tyre?...
YES it is important... very important.... thats the whole thing... if air is tight .. the rolling ristance won't produce a lot of friction. If its lose... air inside circulates at lower speed than the tyre... causing friction.

Its for you to buy it or not... I don't have any references.

[SLK]

found a discussion http://www.physicsforums.com/archive...p/t-37939.html
its all mixed up as its a forum too.

anyways.. after some more reading... I can say ...
for road cars better to use higher pressure.
for track racing with racing tyres... use low pressure.

whatever it is.... lets not discuss it anymore on this thread.

Though it'll be good if some mod could put some of these last posts in a new thread.

[Kaizer Sozay]

Guys normal petrol costs 55 bucks & speed 97 just 60 bucks, earlier the difference was rs 10 now its down to rs 5, Dosnt it make more sense to just tank up on 97. Suddenly i dont feel the pinch as the diffential is only 5 bucks.

[condor]

After the near OT discussion of tyre pressures ...
Use Shell, since I can get it in Bangalore. Outside, I try to top up at any Reliance.

One imp point with fuel from both of these is that the fuel is base-line fuel. And not the Power/Xtra-Premium/Speed/Turbo-Jet variety - but still gives very good FE. Engine also runs smoother. The difference was noticeable even the first time I filled Shell.

OT, went to a pump near St John's in BLR. Asked for Speed. The guy says "take this sir, it is Hi-Speed", trying to make me get his regular diesel wile I asked for Speed Diesel. LOL. Diesel is HSD [Hi-Speed Diesel].

[Technocrat]

Originally Posted by Kaizer Sozay

Guys normal petrol costs 55 bucks & speed 97 just 60 bucks, earlier the difference was rs 10 now its down to rs 5, Dosnt it make more sense to just tank up on 97. Suddenly i dont feel the pinch as the diffential is only 5 bucks.

I disagree its not jewellary which you would buy now because its cheap now. You should also check whether your engine needs a 97 octane fuel or not

[rks]

Originally Posted by Beeman

i would love to use a higher octane fuel but i heard the engines in cars for india have been specially calibrated to run on lower octane fuels so higher octane might be damaging......
Any thoughts on this anyone??

Here is an excellent website:

http://www.fuelsaving.info/fuels.htm

This expert advises that higher octane fules cannot do any harm on most modern vehicles:

One common misunderstanding is that using a higher than intended octane fuel is actually bad for performance and economy, because it "is too hard to burn" or "burns too slowly". In fact this is wrong; unless the ignition system is extemely marginal, using high-octane fuel in an engine designed for low octane should not cause any problems.

This expert also says the following:
In general high octane fuels can be beneficial if your car has an ECU with a knock sensor. Secondly high octane fuels are denser and so contain 2-3% more fuel, so that should improve mileage as well.

See also the following website:

http://www.carbibles.com/fuel_engine_bible.html

I have voted for Speed 97 based on the above considerations. I use just Speed most of the time but whenever I have the chance I use Speed 97 from the BP bunk near King's Circle Garden (Matunga). This bunk doesn't adulterate and the attendants there are very particular about verifying zero and completion as well. I think I have found some improvement in mileage with Speed 97 but not too noticeable.

[quake6]

I filled the premium petrol from an indian oil pump and found no difference in the performance of my 2 month old santro xing(eRLX)..The mileage(15kmpl) I got was the same as that given by regular unleaded fuel.
The manual does not specify anything regarding adding additives (like system G) or filling high octane fuel.

The dealer guys mentioned that I should generally fill petrol from just one pump and continue with it.

My questions:
1.Do high octane fuel or additives give any performance/mileage boost in mpfi cars which are new ?
2.Why do we have to stick to one pump for filling up the petrol?

btw: I'm back to using regular unleaded(HP) and it continues to give me a mileage of 15kmpl in the city with ac on.I generally drive conservatively (no excessive revving or speeding) .

[sandeep108]

Originally Posted by quake6

I filled the premium petrol from an indian oil pump and found no difference in the performance of my 2 month old santro xing(eRLX)..The mileage(15kmpl) I got was the same as that given by regular unleaded fuel.
The manual does not specify anything regarding adding additives (like system G) or filling high octane fuel.

The dealer guys mentioned that I should generally fill petrol from just one pump and continue with it.

My questions:
1.Do high octane fuel or additives give any performance/mileage boost in mpfi cars which are new ?
2.Why do we have to stick to one pump for filling up the petrol?

btw: I'm back to using regular unleaded(HP) and it continues to give me a mileage of 15kmpl in the city with ac on.I generally drive conservatively (no excessive revving or speeding) .

1. The difference may not be so noticeable in some cars - it all depends on how the ECU, etc. handles it. On both swift and ohc, I definitely found xtra premium to be much better than normal petrol - more low end grunt, smoother engine, etc. Not too sure about FE though, it was mostly same. Speed felt in between normal/xtra premium.
2. Not really. It is just better to stick to one pump for consistently determining mileage, fuel adulteration/quantity, etc. problems. I have mentally earmarked a few pumps and usually do not try and experiment.

Actually using the better fuels avoid injector cleaning, gumming, etc. longer term benefits rather than mileage improvement.

[quake6]

Originally Posted by sandeep108

Actually using the better fuels avoid injector cleaning, gumming, etc. longer term benefits rather than mileage improvement.

Yes I'm aware of the above but from a purely economics point of view
if I fill up (tank full) unleaded fuel 2 to 3 times and then say get a tank full of the premium stuff and repeat this cycle will I be able to get the benefits you mentioned?

[s.prashanth]

Originally Posted by S@~+#0$#

I voted for Shell as I run my esteem on Shell Super petrol.
Shell(atleast in Bangalore) has set a standard and has changed the entire experience for a person going to a petrol pump for a refill. They greet you with a Namaskar, always give you a bill and the Quality and Quantity are very good.

Is this the same in other cities as well, I really hope it is and other oil companies should follow suit.

Shell does not have arefinery in India it is BP who siupply the fuel which later branded as shell, regarding quantity, all new dispensers give correct quantity in any fuel pump, it is the time of day u fill that makes a difference, fill after 10pm and you will get a differnce in fuel average

[sandeep108]

Yes, time of day matters. Late night/early morning when it is cooler, you will get more fuel, since it is denser.

Alternating between ordinary and speed/power/xpre would also help, I used to do that, never had any clogged injector/fuel pump.

But I do believe that for metros, now on BH III, ordinary petrol itself is supposed to be 89octane, up from 87. Correct me somebody if I am wrong.

[shazikon]

I have tired Shell, BP (speed and Speed 97), HP and IOC.. I feel Speed 97, shell super, Speed, IOC xtra prem, HP are the best fuels in that order..
My ikon has a Kn filter, irriium plugs, and plug wires, a custome header and a free flow exhaust..
With Speed 97- i get around 14KMPL while driving inthe city (mostly on the ring roads) with intermittent AC on. + super smooth performance and pickup
Shell Super - i get around 11.5 - 12 KMPL in same driving conditions.. engine not as smooth as with Speed 97. performance is pretty good
I have stopped using IOC xtra prem and HP now as they dont come any where near this perofrmance.
i know with my ikon 1.6 there should not be much diff with a higer octane fuel but here are hte real facts!