Petrol Question

[jaylah]

Not sure which section this post should be in.

My question is: If my car is 91RON compatible (as in it says that on my fuel cap), and I use 98RON. Do i get more power out of the 98, or is it exactly the same as the 91? I read somewhere that i should use what it states as that will give me the best performance. =S

Any help? Thanks!

[Fredoops]

you will get more power out of the 98

[mocchi]

you will get more power out of the 98

no you dont.

[Fredoops]

no you dont.

Thats not entirely true.

I distinctively remember some vehicles gives you two different power figures in their brochures, one figure for ULP and one figure for PULP.

The Holden TS series Astra is a prime example of this.
Even my CL9 euro responds differently between 95 octane and 98 octane. and that's only a difference of 3.

Here I quote a post form whirlpool i saw last year:

User #15607 16408 posts
Turbo B
Whirlpool Forums Addict


The way an engine works (one designed for these fuels), is that the engine computer monitors all these different settings, from the AFM/MAF (air intake), to the O2 sensor (exhaust gas), to knock sensors (remember here, we are talking cars DESIGNED FOR use of the higher octane fuels), and numerous other sensors around the engine.

If you fill the car on 91 Ron, the AFM, O2, and Knock will have a certain value.
When the engine is started, the engine computer will advance the timing up to 2 -3 degrees, and monitor knock values, if detected, the ECU will retard the timing back slightly until the values are within acceptable limits. Mainly the Knock sensor in this equation will show that when you step on the go-pedal, the engine will start knocking earlier, so what the engine computer does is 'retard' the timing on the engine slightly more to reduce this knocking effect. This retardation will reduce performance somewhat.

knock: in spark-ignition internal combustion engines occurs when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front. The fuel-air charge is meant to be ignited by the spark plug only, and at a precise time in the piston's stroke cycle. The peak of the combustion process no longer occurs at the optimum moment for the four-stroke cycle. The shock wave creates the characteristic metallic "pinging" sound, and cylinder pressure increases dramatically. Effects of engine knocking range from inconsequential to completely destructive.
(Thanks Wiki)

Now, when you run 98 Ron (or higher) fuels, the engine computer does the same thing when started, it advances the timing up to 2 – 3 degrees, this enables the maximum 'factory' limited power to be developed from the vehicle's engine. If, again the knock sensor reports too much knock, the timing will be retarded slightly to reduce pinging.

98 Ron fuels are better formulated to withstand the harsh environments of the cylinders, therefore better avoid this pinging effect, and thus timing on a performance engine will remain further advanced on 98 ron, than it will on 95 or 91 ron fuels.

Remaining further advanced means the engine can develope higher power levels without the potential for damage.

Links:
Here are some links to some of the effects that pinging/knock/detonation have on an engine...

http://w6rec.com/duane/bmw/piston/piston2.jpg
http://www.aa1car.com/library/piston...ion_damage.jpg

Comparison of good vs bad:
http://bedwani.com/turbohonda/crx-bd-pist3.JPG

B.

anchor: whrl.pl/RbXEny
posted 2009-Jul-31, 8am AEST

[da12nv]

you do get a little bit more power and the fuel is alot cleaner therefore better for your engine, also you should get more kms to a tank using 98ron

[mocchi]

Thats not entirely true.

I distinctively remember some vehicles gives you two different power figures in their brochures, one figure for ULP and one figure for PULP.

The Holden TS series Astra is a prime example of this.
Even my CL9 euro responds differently between 95 octane and 98 octane. and that's only a difference of 3.

Here I quote a post form whirlpool i saw last year:

haha nice comeback. +1 for you.
what is true in your case, may not true for other cars.
what about other cars that cannot advance timing? will it run better with higher octane? hehe dont think so.
http://www.ftc.gov/bcp/edu/pubs/cons...tos/aut12.shtm

[mocchi]

btw, octane rating varies all the time by few points.
when you buy 91, it wont be 91. might be 90 or 92 depends on temperature and the mix.

[Phased]

You gentlemen are missing out on a greater perspective here. Well a few actually...

Firstly, although a higher octane fuel has more resistance to compression, temperature and knock which can allow for a higher level of advanced timing which in turn can increase power... A higher OCTANE rated fuel contains less combustible energy per comparable volume. Gains can only really be noticed when you can take the Timing/Fuel maps outside of standard ECU Limits ie. Custom Tuning.

Secondly, Standard cars although may react to a higher octane fuel... it will react minimally. The standard ECU has fairly conservative limits for advanced timing to sustain engine longevity and drive-ability.

The difference may be more noticeable in a modern car. ie. post 2005 OBD IIb Vehicles. However the main principals still apply.

If you were to tune your car to 98 octane... then this would be a different story. You are then telling the ECU specific values to advance timing outside of its standard limits. Even then... if you tune a completely standard car and the only difference is the Octane rating of fuel... you will notice minimal gain. The most part of gains from standard cars are detuning for emissions and slightly conservative (ie. Rich) fuel maps for longevity/driveability.

[Chr1s]

Well, by a purist definition;

You can be more scientifically correct and say that the octane rating of a fuel is its ability to resist knock, rather than mention temperature and compression as those two are a function of knock. But it helps to mention the other two if people don't understand what knock is.

My input, on a honda ECU, no you won't see any great benefits paying an extra 20cents per litre at the bowser for that premium awesomeshit. This may be argueable, but in theory it shouldn't help.

[mooshie]

I think that we should ask the OP what kind of car he has?

Cant make sweeping statements as they are not applicable to all cars. Phased and Chr1s have got the general answer though.

A tank of 98 is good to run through a standard car every now and then as it has 'detergents' in it that help to clean out the gunk in the same way that fuel additives do but at a hell of a lot cheaper price.

[gumus89]

I think that we should ask the OP what kind of car he has?

Cant make sweeping statements as they are not applicable to all cars. Phased and Chr1s have got the general answer though.

A tank of 98 is good to run through a standard car every now and then as it has 'detergents' in it that help to clean out the gunk in the same way that fuel additives do but at a hell of a lot cheaper price.

It also depends who you buy it from. Because the Caltex 95 is meant to have the same detergents as their 98 unlike BP with their 95 and 98 Ultimate.
Most cars dont have the capability to advance timing, only retard. So in most cases, going above and beyond the factory minimum is a waste of money.
You will not see better economy or performance. And if you do, its most likely placebo effect.

[Holy Frog]

I ran 95RON in my non vtec 94 accord.

Not only did it run more efficiently - giving me more range, it also smelled nicer out of the tail pipe, and after 60,000 of fairly hard driving, the engine still was as sweet and strong as ever, maintained 9.0 0-100kmh, and did not puff any smoke after 19 years.

My VTEC 2008 Jazz, VTEC 2012 Accord Euro and Lawnmower all run premium. Yes Lawnmower. I ran 2 tanks of regular in it recently and it was noticeably smellier and louder. (carbon Monoxide smell)
My Victa is no 5.5 years old and hasn't missed a beat.

Although other factors may be involved, I like to use the better fuels.