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lower than stock evildoer
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Discussion Starter · #1 ·
Hi,

the gas station where I usually refill my tank replaced the 98-octane unleaded fuel with 100-octane (they call it super 100). They say it can be mixed with any other fuel. The new fuel increases engine power by about 3%, reduces consuption by about 4% and it's 100% sulphur free.

After couple of miles the car was a bit lazy but now I think the engine power is more elastic and more explosive.

Is it OK to use it? (the manual recommends unleaded 98-octane) :confused:

btw ... i`m aware that you have different standards, so maybe this will help:

 

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closer2pin said:
It's a waste of money in my opinion. :thumbdwn:
Agreed. Engines are designed for a particular octane, if its gets less than that, preignition occurs which can be damaging, so the car retards the spark which then robs power. If it gets the right octane, there are no problems. If it gets "extra" octane, there are no problems, but no benefits either. The drawback to extra octane is cost.

BTW, some cars do run better with higher octanes than rated as required by the manufacturer, typically those with after-market turbo/superchargers.

Bill
 

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gerchy said:
Hi,

the gas station where I usually refill my tank replaced the 98-octane unleaded fuel with 100-octane (they call it super 100). They say it can be mixed with any other fuel. The new fuel increases engine power by about 3%, reduces consuption by about 4% and it's 100% sulphur free.

After couple of miles the car was a bit lazy but now I think the engine power is more elastic and more explosive.

Is it OK to use it? (the manual recommends unleaded 98-octane) :confused:

btw ... i`m aware that you have different standards, so maybe this will help:
Yes it´s ok to use it.
My car consumes less fuel when i run Shells 100 octane when im visiting Germany.
Im not sure if there are any poweradvantages, but just the fact that it consumes less makes it fine with me.
Higher octane does usually equals less consumption, at least that is what my experience says.
My car consumes the most with 95 octane, less with 98 and even less with 100 octane (RON).
 

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lower than stock evildoer
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Discussion Starter · #5 ·
It`s not a waste of money. The price is the same. They REPLACED the regular 98-octane with this one so now you can buy 95 and 100 octane. Unless if you visit another gas station. :thumbup:
 

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The science of octane ratings has been covered in detail many times.
Specifically, fuel of a higher octane rating resists detonation more than a fuel of a lower octane rating.

Unfortunately, not everyone agrees on the practical interpretation of that irrefutable science.

My long-held IF-THEN interpretation (yours may be different) is simply:

IF:
- If the car didn't detonate prematurely (aka "ping") on the original fuel ...

THEN:
- Using fuel of any higher octane can't possibly increase engine performance (aka power); nor can it possibly increase efficiency (aka distance per gallon)

 

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Then how can you explain the fact that our cars are running better fuel economy and more power with higher octane fuel?
 

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Prove it.

If indeed you're making more power/better mpg on higher octane fuel one of two things is happenning:

1. USA cars are detonating regularly on 93 octane gas
2. USA cars have a different fuel/timing map for lower octane gas.

Octane itself does NOT create power. All it does is allow for a slower burn. The advantage of this is that you can run more timing advance at WOT without preignition. More timing advance across the board = better gas mileage. If you've ever tuned a standalone for street driving you can see that at cruising speeds on the highway, some Hondas will run at ridiculous advance... up to 45+ degrees. This increases combustion chamber temperatures and pressures allowing for a leaner more fuel efficient charge.

But like I said, if the fuel/timing map is optimized for 91 or 93 octane for no preignition, putting in 100 octane is not going to do anything.
 

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boostd4 said:
Prove it.

If indeed you're making more power/better mpg on higher octane fuel one of two things is happenning:

1. USA cars are detonating regularly on 93 octane gas
2. USA cars have a different fuel/timing map for lower octane gas.

Octane itself does NOT create power. All it does is allow for a slower burn. The advantage of this is that you can run more timing advance at WOT without preignition. More timing advance across the board = better gas mileage. If you've ever tuned a standalone for street driving you can see that at cruising speeds on the highway, some Hondas will run at ridiculous advance... up to 45+ degrees. This increases combustion chamber temperatures and pressures allowing for a leaner more fuel efficient charge.

But like I said, if the fuel/timing map is optimized for 91 or 93 octane for no preignition, putting in 100 octane is not going to do anything.
Nice summary.

Bill
 

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I think you need look at the chart the original poster included and realize that he is not in the US. 100 RON is equal to about 95 octane R+M/2 according to the chart posted. My wife's lexus owners manual states 89 octane is the minimum, but "better performance and improved fuel economy can result from higher rated fuels." I think there is a window where you could make a little more power with a little higher octane. Are bmw's knock sensors pulling back timing with 93 octane, perhaps. In california on 91, i'd say very likely. With my M5 on 91 octane, i get a split second of detonation if i stomp on the gas pedal when the rpms are between 2-3k rpm that I can hear. On a dyno, there is a dip in the torque curve in this range too, which i think might be attributable to knock sensors pulling back the timing. 91 is the minimum octane recommended for my car, but it sure does feel stronger and does get a little better mpg when i mix in a half a tank of 96 at the track (plus no pinging). Next time i have a chance to dyno, i'll try it with higher octane fuel to see what happens. Several years ago, at a dinan tech event, someone asked the easiest way to get more hp out of an M5, steve dinan responded "100 octane fuel, the electronics will do the rest." He was discussing bmw's dme adaptation abilities.
Mike
boostd4 said:
Prove it.

If indeed you're making more power/better mpg on higher octane fuel one of two things is happenning:

1. USA cars are detonating regularly on 93 octane gas
2. USA cars have a different fuel/timing map for lower octane gas.

Octane itself does NOT create power. All it does is allow for a slower burn. The advantage of this is that you can run more timing advance at WOT without preignition. More timing advance across the board = better gas mileage. If you've ever tuned a standalone for street driving you can see that at cruising speeds on the highway, some Hondas will run at ridiculous advance... up to 45+ degrees. This increases combustion chamber temperatures and pressures allowing for a leaner more fuel efficient charge.

But like I said, if the fuel/timing map is optimized for 91 or 93 octane for no preignition, putting in 100 octane is not going to do anything.
 

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And if it can be heard as in Mikes case here im quite sure it has been going on before that and the sensors adapted.
I really don´t have anything else but my own experience to rely on here, but to me it is a fact that my car runs better on 100 octane fuel then 98 and 95.

But that put aside for a while, what gerchy wanted to know was if it is ok to use, and that answer is yes.
Can we all at least agree on that?
 

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lower than stock evildoer
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Discussion Starter · #12 ·
Hmmm ... I think it`s OK to use it. I asked several mechanics that I find very reliable and they all agreed it can be used. Like the chart says, it`s the PON value that matters so it would be good to know what`s the "pump octane number" of this 100-octane (RON) fuel.

I don`t know if this is a psycological thing, but I think the car runs better - it offers more power and it revvs quicker .... :dunno:
 

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gerchy said:
Hmmm ... I think it`s OK to use it. I asked several mechanics that I find very reliable and they all agreed it can be used. Like the chart says, it`s the PON value that matters so it would be good to know what`s the "pump octane number" of this 100-octane (RON) fuel.

I don`t know if this is a psycological thing, but I think the car runs better - it offers more power and it revvs quicker .... :dunno:
A little OT question, but where is your location? What does SI stand for? I don't even know if you are talking about amrican gas here... :dunno:
 

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So, in summary, higher octane fuel will not hurt your car. Worse case is that it will hurt your wallet without any extra return that one might hope to get.
 

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tsaros said:
What gerchy wanted to know was if it is ok to use, and that answer is yes.
Can we all at least agree on that?
Yes.
As I interpret the irrefutable part of the science (your interpretation may differ) ...

Burning fuel with a higher-octane rating than necessary to not cause pinging (or to cause the knock sensors to retard timing) can not possibly harm the engine.

Thought about in a slightly inaccurate and a bit too-simple sense, slower-burning fuel never hurt anyone. :)
 

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The E46 M3 shows real gains on a dyno up to 96 octane with stock software. If you've got an Evo or an STi, you gain one hell of a lot of power runnign 100 octane.
 

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Nick325xiT 5spd said:
If you've got an Evo or an STi, you gain one hell of a lot of power runnign 100 octane.
How can that possibly be?
Assuming you are talking AKI numbers, is the engine actually pinging (i.e., therefore running retarded) at less than 100 AKI?
 

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shaftdrive said:
How can that possibly be?
Assuming you are talking AKI numbers, is the engine actually pinging (i.e., therefore running retarded) at less than 100 AKI?
Short answer: Yes.

Long answer: I've personally seen these vehicles gain 10MPH at the end of the Summit Point Main Circuit straight. Same day, same car, same software, same driver. FI LOVES high octane.
 
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