Peckster

Toluene. Do a search here or on the turbo board, there's been lots in the past.

PCMAX

The US delivered cars were obviously detuned to run on lower octane rated fuel, probably something to do with your emission laws. I know that the HP output varies from the US to the rest of the world.
My Australian delivered vehicle has a factory sticker inside the gas filler access panel that reads "OKTAN MIN 98 ROZ/RON". The premium unleaded fuel sold here by both SHELL & MOBIL (Exon) is rated at 98 octane & my car runs like a dream on it. It is up to 10 cents per liter more expensive.
(Our premium fuel is about $3.29 USD per gallon) I haven't tried to use the standard stuff because for the equivalent of saving 15.5 cents US per gallon its just not worth it.
C'mon you guys it's a Porsche treat it like a lady!!

dualblade

is euro98 from the same rating system as america uses? is your 98 equivalent to what 98 would be on our system or is it something different? i've heard of different regions using different systems so i was thinking maybe your 98 is like our 93. if your 98=our 98, why doesn't europe use lower grade gas to drop gas prices down a bit?

ERAU-944

andrew there is a ~5 pt difference or so in the fuel grades. his 98 is equivalent to our ~93. the 8v n/a cars (up till 88) run on 87 octane in the states.

-Michael-

88BlueTSiQuest

Octane is simply a measure of a fuels resistance to burning. The higher the octane, the hotter the combustion or spark needed to ignite it.

Adding a higher octane fuel to a low compression engine, and not changing the engine timing or spark plug temp could result in unburned fuel and lower performance/gas mileage. Don't flame me, I said "could"

The reason higher compression, and turbo/supercharged motors require a higher octane is due to the higher combustion chamber temperatures caused by the higher compression. The higher temp can cause pre-ignition, knock, ping or detonation(what-ever you wish to call it), which can burn a whole in pistons. Higher octane withstands these conditions, and won't ignite until ignited.

I run 87 in the 944, and 91(highest available around here) in the GTP and Conquest. When I'm racing the Quest, I use alcohol injection to increase octane and promote cooling of the combustion chambers.

Toulene is the main ingrediant in most of your 'Octane Boosters' you can buy at the store. The only real issue there is the amount of Toulene in those little bottles. It takes a heck of alot more than merely 8oz. of watered down Toulene to see any real octane change. Check out some of the Grand National websites, they have great write ups and calculator's for determining cheap ways of increasing octane using Denatured Alcohol(this info should really only pertain to 951's).

jamiejim

I was told by a respected Porsche mechanic that in hot weather areas like
Arizona to use higher octane in summer, but 87 is ok in cooler months. Makes sense if higher octane ignites at higher temperatures, this would eliminate ping from using lower octane when the outside temperature is 110 degrees.

gleamingred944

Just to note that, here in Canada at least, high octane gas evaporates faster than low octane. (I say 'here in Canada' because octane is significantly affected by additives, and other countries probably use different additives.) If you have a hand-started snowblower here, you learn very fast to use premium in it at 30 below!

Furthermore, again in Canada at least, the 'octane' listed on the pump means one thing in winter, another in summer - the summer gas is required to be lower octane to reduce evaporation and the feds have simply legislated their own meaning of octane.

Here, the major brands get their own mixes direct from the refineries in Montreal, so what you get is consistent. The minors grab from wherever they can, frequently from a tail-end load, so are less consistent. Again, may be different elsewhere.

RedlineMan

Hey All;

- Octane keeps an engine from detonating, period.

- Higher octane gas actually has LESS energy than lower octane gas.

- S2s and Turbos (or anyother so equipeed) will run better on higher octane fuel because in hard use their knock sensors will retard timing if detonation is detected. Retarded timing means less HP.

The DareDevil

With the wind-chill it is about -40c here in Montreal today. All my cars are full with 91 octane grade fuel.

Also, I get better fuel mileage when using high-octane fuel.

Damian in NJ

I use Sunoco 93 in my car.

97xray

Maybe it IS in my head, but it's in my ears too;
I heard knocking the one and only time I put 87 in the Euro.
Since then, under the greatest loads I could give the engine - and with 93 octane - not a sound but the good stuff from the engine.
So, yeah, I guess it "could" be in my head, but the >10:1 compression does seem to notice lower octane.

944S2NUT

92 Min for the S2. I always put 94 in. It is in the manual

'86 944 turbo

I use Sunoco 94 all the time in my car. On a turbo car higher octane makes a big difference.

deni durrell

We (in the USA) have a lower octane rating for our engines due to the fact that PAG knows that we often use questionable fuel (um, inferior).

Nonetheless I use 91 (highest commerically sold here in Ca) in my NA as I've noticed that the engine revs lower at higher RPMS. The is a distinct difference that is quantiatively measurable. When I use use 87, the car is not as responsive and revs higher at speed.

Nonetheless, I feel like I am repeating myself, this has been discussed 50 billion times here at Renn's Diner.

944S2NUT

Looks like it will be discussed a 50 billion more times!