Rennteam 2.0 - EN - Forum - Re: Octane 95, 98 or 100 ? - Page1

Apr 26, 2006 6:58:59 AM

BangoO: Pilot; Loc: France , France; Posts: 366, Gallery; Registered on: Apr 22, 2006

Octane 95, 98 or 100 ?

Hi everyone,

I found this great forum some days ago and finally came up with a question

I have a 987 Boxster S since 3 weeks now, and I was wondering about the octane to be used.
On the tank, it says I should use 98.
The Porsche reseller told me 95 was ok.
Now, in Switzerland (I'm french, but I work in Switzerland), there is also 100 available.

The obvious question is... is using 95 ok ?
I remember testing both 95 and 100 on my previous car (Z4 3.0) and could not notice any difference in performance... should I notice any with the 987 Boxster S ?

Thx for the help !
BangoO

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Apr 26, 2006 7:40:28 AM

dreamcar: Rennteam VIP; Loc: Hampshire , United Kingdom; Posts: 8797, Gallery; Registered on: Apr 19, 2004; Reply to: BangoO

Re: Octane 95, 98 or 100 ?

Welcome to the Rennteam family

Up until recently I've always used Shell Optimax (98 Octane). I've just come back from a few days in Germany where I used 95 Octane fuel (BP and Shell) and I could tell no difference in either performance or fuel economy - after filling up in convoy with porsche-jeck we cruised at an effortless 250 km/h on the Autobahn - fast enough for me! One thing I would not do is use cheap supermarket brand fuel, except in an emergency, it is cheaper than Exxon / Shell / BP etc for a reason, it might comply with the octane rating but the additives that the premium brands add are missing. Fuel economy and performance suffer, even in a basic car. I am not sure, but I don't believe there would be any advantage in using 100 octane fuel over 98. I stand to be corrected on that last point, however?

Some say that the car may need more frequent servicing if using the lower octane fuel, but I've not had that confirmed from an "official" source.

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Apr 26, 2006 9:15:48 AM

Steven Martins: Junior; Loc: Oporto, Portugal; Posts: 145, Gallery; Registered on: May 10, 2004; Reply to: dreamcar

Re: Octane 95, 98 or 100 ?

Quote:
dreamcar said:
Up until recently I've always used Shell Optimax (98 Octane). I've just come back from a few days in Germany where I used 95 Octane fuel (BP and Shell) and I could tell no difference in either performance or fuel economy

Some time ago I also did a comparison between 95 and 98 and I couldn't find any "visible" difference. I'm sure one is able to notice a difference when driving hard but that's not the case with our day-to-day driving.

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Apr 26, 2006 11:56:57 AM

BangoO: Pilot; Loc: France , France; Posts: 366, Gallery; Registered on: Apr 22, 2006; Reply to: Steven Martins

Re: Octane 95, 98 or 100 ?

Thx for the answers, and thx for the welcome

That's what I thought, I'll continue using 95 Octane as it is much cheaper...

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Apr 26, 2006 1:41:55 PM

edz: Rennteam Pro; Loc: South Orange County; Posts: 2022, Gallery; Registered on: Oct 11, 2005; Reply to: BangoO

Re: Octane 95, 98 or 100 ?

If you use high octane 100+ gas, keep in mind that prolonged use may eat the engine seals. So alternate between lower and higher octane.

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Apr 26, 2006 3:26:04 PM

mcdelaug: Expert; Loc: Fort Worth, Texas , United States; Posts: 1919, Gallery; Registered on: Mar 3, 2004; Reply to: edz

Re: Octane 95, 98 or 100 ?

If your tank says use 98 octane, that is probably the lowest octane your engine management system requires to use its most aggressive timing map. Using lower octane fuels typically results in a less agressive map being used by the DME if any preignition is detected. Whether you would notice a performance difference from this is difficult to say and would obviously depend on the driver's sensitivity and driving style. Conversely, using a higher octane fuel than the tank recommends would probably have no performance benefit since most agressive map is already being used at 98 octane. Higher octane fuels are more important in cars with forced induction (turbos or superchargers) since preignition is a bigger concern in these cars, especially if they have been modified for higher performance.

In my opinion, for an unmodified, normally aspirated car that says "use 98 octane", 98 octane will be the cheapest fuel that will consistently give you the car's maximum output.

mcdelaug

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Apr 26, 2006 7:20:03 PM

Yan: Newbie; Loc: WA; Posts: 20, Gallery; Registered on: Aug 3, 2005; Reply to: mcdelaug

Re: Octane 95, 98 or 100 ?

I wouldn't worry... engineers designed it for 93 so anythign above that is good. Here on the west coast of the US the max I can find is 92; I'm glad the engine management can handle down to 91octane... send me some of that 95 if you would!

BTW, rive gauche? I lived in Prevessin for many years... I wish I had my Cayman over there...

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Apr 26, 2006 7:38:01 PM

The Groom: Expert; Loc: EU; Posts: 1779, Gallery; Registered on: Jan 23, 2005; Reply to: Yan

Re: Octane 95, 98 or 100 ?

Yan, keep in mind that US rating = (RON + MON) / 2, whereras we only advertise RON in Europe. Basically, EU rating = US rating + 5.

So BangoO was talking about 90, 93 or 95 octane. 95 octane is pretty rare though, I think only Shell carries it, and not even in every station.

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Apr 27, 2006 6:48:37 AM

BangoO: Pilot; Loc: France , France; Posts: 366, Gallery; Registered on: Apr 22, 2006; Reply to: The Groom

Re: Octane 95, 98 or 100 ?

I was talking about 95, 98, and 100

In France, you only find 95 and 98, nothing else.
But you find them everywhere.
In Switzerland, where gas is cheaper, there are 95, 98 and 100 (to my knowledge, Shell only).

Yan, I leave in France, on the other side, and I work in Geneva.

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Apr 27, 2006 4:02:54 PM

boubou: Junior; Loc: Brussels , Belgium; Posts: 52, Gallery; Registered on: Dec 12, 2004; Reply to: BangoO

Re: Octane 95, 98 or 100 ?

I was told that it could damage your enige driving with lower than 98 octane. The engine electronics are optimised for this fuel and other fuels -oin the long run will disturb your pre-ignition. since the flashpoint is different in lower octane you might get some funny noises at low rpm & during cutt-off. I only use 98.

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Apr 27, 2006 5:38:39 PM

dreamcar: Rennteam VIP; Loc: Hampshire , United Kingdom; Posts: 8797, Gallery; Registered on: Apr 19, 2004; Reply to: boubou

Re: Octane 95, 98 or 100 ?

Quote:
boubou said:
I was told that it could damage your enige driving with lower than 98 octane. The engine electronics are optimised for this fuel and other fuels -oin the long run will disturb your pre-ignition. since the flashpoint is different in lower octane you might get some funny noises at low rpm & during cutt-off. I only use 98.

Don't think so. The engine is fitted with cylinder-specific knock control which adjusts timing etc to compensate for different fuel grades. I'll now wait for Fritz to shoot me down on this one?

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Apr 27, 2006 7:25:33 PM

percymon: Senior; Loc: Chester; Posts: 765, Gallery; Registered on: Aug 23, 2005; Reply to: dreamcar

Re: Octane 95, 98 or 100 ?

95 ron invokes the knock sensors, and also doesn't produce full power (how much less is debatable).

I've run one tank of 95 in my 987S and the car didn't like it at all, so Optimax only for me.

My previous 986 ran better on 98RON, and did approx 10% more mpg (albeit mainly short runs), so the 6% extra cost was easily recovered.

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Apr 27, 2006 8:38:05 PM

GR: Senior; Loc: S Bucks, England , United Kingdom; Posts: 779, Gallery; Registered on: May 17, 2005; Reply to: percymon

Re: Octane 95, 98 or 100 ?

Anyone going to try BP's new 102 RON super-super unleaded? Shame is Pounds2.42 a litre

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Apr 27, 2006 8:52:19 PM

BangoO: Pilot; Loc: France , France; Posts: 366, Gallery; Registered on: Apr 22, 2006; Reply to: GR

Re: Octane 95, 98 or 100 ?

After reading all this, it's not easy to make a choice

Can you guys confirm the extra miles using 98 ?
What about 100 then ?

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Apr 27, 2006 9:20:29 PM

dreamcar: Rennteam VIP; Loc: Hampshire , United Kingdom; Posts: 8797, Gallery; Registered on: Apr 19, 2004; Reply to: BangoO

Re: Octane 95, 98 or 100 ?

Quote:
BangoO said:
After reading all this, it's not easy to make a choice

Can you guys confirm the extra miles using 98 ?
What about 100 then ?

I've not noticed either a drop in power or an increase in fuel consumption when switching grades, even if up until now I've mainly used Shell Optimax (RON 98)

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Apr 28, 2006 4:09:55 PM

percymon: Senior; Loc: Chester; Posts: 765, Gallery; Registered on: Aug 23, 2005; Reply to: dreamcar

Re: Octane 95, 98 or 100 ?

I tried the Tesco 99RON super-unleaded and that got me less mpg than Opotimax on a motorway run - not sure what that says, but super unleaded in particular goes off while in storage, so maybe the Tesco store was a low volume seller and the octane had dropped ??

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Apr 28, 2006 4:39:22 PM

dreamcar: Rennteam VIP; Loc: Hampshire , United Kingdom; Posts: 8797, Gallery; Registered on: Apr 19, 2004; Reply to: percymon

Re: Octane 95, 98 or 100 ?

Quote:
percymon said:
I tried the Tesco 99RON super-unleaded and that got me less mpg than Opotimax on a motorway run - not sure what that says, but super unleaded in particular goes off while in storage, so maybe the Tesco store was a low volume seller and the octane had dropped ??

See my comment above in this thread regarding supermarket fuel. You've just confirmed my own findings. Don't use it. Stick to premium brands such as Esso, BP, or Shell. It comes out of the same refineries but IT IS NOT THE SAME FUEL. I'd rather use 95 RON premium brand fuel than 98RON or even 100RON supermarket fuel.

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Apr 28, 2006 6:02:42 PM

GR: Senior; Loc: S Bucks, England , United Kingdom; Posts: 779, Gallery; Registered on: May 17, 2005; Reply to: dreamcar

Re: Octane 95, 98 or 100 ?

Definitely, its always been a generation or 2 behind the main brands

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May 11, 2006 1:16:36 PM

Porsche-Jeck: Rennteam Master; Loc: Rheinland , Germany; Posts: 4856, Gallery; Registered on: Jun 27, 2005; Reply to: BangoO

Re: Octane 95, 98 or 100 ?

Quote:
BangoO said:
After reading all this, it's not easy to make a choice

Can you guys confirm the extra miles using 98 ?
What about 100 then ?

Indeed, seems to be a special science

I just learned that the expensive 100 Octane stuff (in Germany available only at Shell and Aral stations) is pointless for our Boxsters - to exploit the claimed advantages of the 100 stuff, you would need an engine with a higher compression.

Judging from the manual the Boxster's engine can live with both, 95 or 98 octane - I don't know whether one can feel a performance difference

I'll stick to the 98 stuff anyway (myself preferring the higher refined stuff also when choosing a nice drink

)

Though I didn't understand edz61's comment about the 100+ gas possibly causing damage to the engine's seals

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