Gasoline Octane

[Belledan]

Can anyone confirm if the 986 ( mine is a 1998) can be safely run on 87 or 89 octane? The manual suggests that lower ocatne can result in engine "damage". They put quotes around this which makes me wonder why they are qualifying the word damage, A recent find on the internet discoverd the follwing from Porsche's own engineers...

All Porsche engines are designed for premium, too, but it's not available everywhere. "Our cars must be able to drive all over the world, and so we are able to run on regular," says Jakob Neusser, director of powertrain development at Porsche's research and development center in Weissach, Germany. "You don't have to feel that a mechanical problem or anything else will happen" using regular gas, even in the highest-performance, regular-production Porsches.

[Adam]

Why risk it? The boxster engine is under pretty high compression and using a lesser octane than 90 could potentially cause knocking even with knock control sensor. You should be using 93 Octane for optimum performance. I do know that you can safely use 87 octane on a toyota corrolla however

[Ad Sach]

re: "safely using 87 octane".
On my 94 Sentra, I found the dollars per mile was best using 89 Octane. The recommendation in the owners manual said (surprise) 89 octane recommended.

If you do decide to experiment with 89 octane, check your mileage carefully-there is no point saving 10 cents per gallon is your mileage goes down 8-10%.

There is also no point running 100 octane in a boxster. The electronics won't optimize for anything over 93. I personally can't feel the difference between 91 octane and 93 octane. I've never tried 89 or 87.

The reason I assume one might consider 87-89 octane is economic. I don't bother. I know I could save a lot more in fuel costs by accelerating slowly than I would ever save by purchasing a lower grade fuel. I could also save a lot more by going back to my 94 Sentra.

This car asks for super premium, so thats what I feed her.

Ad Sach

[Laszlo]

This talk about 89 or 93 seems very strange to me as here in Europe, at least for my 2003 S, they recommend 98 Octane. 95 Octane can be used but will lead to less performance, hence why I have never used it.

Maybe these octane differences between the US and Europe explain why petrol is so much more expensive here?!

[Subanez]

I wonder if they measure the octane the same way over there. I know there are a couple of different ways of measuring it, but I'm not sure that would have much difference, anyway.

Just curious, Laszlo, what are you paying per gallon? (I guess it would be per liter, though...) We are all freaking out here because our prices are climbing, but if I remember correctly, prices have always been higher in Europe.

[Laszlo]

I currently pay EUR 0.99 per litre of 98 octane lead-free, with 95 octane maybe being 2-3 cts cheaper.

What about over there?

[Subanez]

Its rougly 4 liters per gallon, a little less. That would put you paying roughly $4.00 a gallon for gas! Holy cow! We pay on average $2.25 for 93 Octane, and as I said, the nation is getting pretty upset.

Maybe we should consider ourselves lucky!

That or we should start a collection fund for our brothers in Europe.

[Laszlo]

I am OK about it as you just get used to it. Anyway, at least it is rewarding to switch on the engine after filling up! I am also lucky in that I have a card enabling me to buy petrol tax-free so at least for me it is not 99cts!

[donv]

There are at least two ways of measuring octane, because the US "CLC" system is actually an average of those two... next time you're at the pump look for the label that says something like:

93 Octane (R+M/2)

they're showing the averaging formula on the pump

The [R]esearch and [M]otor octane measurement systems are defined in ASTM standards in the US (see below). The Research octane number (the one used in at least some portions of Europe) is typically 4 points higher than the US CLC (average) number.

ASTM D2699, "Standard Test Method for Knock Characteristics of Motor Fuels by the Research Method", 1991 Edition.

ASTM D2700, "Standard Test Method for Knock Characteristics of Motor and Aviation Fuels by the Motor Method", 1991 Edition.

[aesir]

In AZ the best octane we get is 91 octane. There are a few places that carry 100 octane. A friend of mine suggested that I pump a gallon of 100 then fill the rest with 91 and I should come out close to 93. Any one have any thoughts on this?

Is it okay to mix octanes like that?

[Subanez]

Thanks for the info, Donv. I've seen the formula, but couldn't remember it well enough to post about it. But I reckon that answers the question! Regardless, they pay a crapoad over in Europe...we should consider ourselves lucky!

[Pilot2519j]

The manufacturers recommendation for the engine is super premium. That is the designed octane for best performance for the engine. I would suggest that you stick with that selection from Porsche. Savings are less than ten cents per gallon for inferior performance.

[JonnyBGood]

Actually, it is $0.99 EUROs per liter. That makes it nearly 4.00 EURO per gallon. The exchange rate from when I went to Ireland 6 months makes it nearly $5-6 dollars per gallon.

And we think WE pay a lot for gas!

[Laszlo]

Also take note that I live in a country where petrol is notoriously cheap at EUR 0.99/ltr!

The Germans, Italians and French are a lot worse off!