93 octane gas only?

[nola mike]

allegedly (it's recommended). i'm sure there'll be disagreement, but i don't think you'll blow up if you run 87. you most likely won't be as fast, and i probably wouldn't flog the car through extreme heat/mountains/etc.

[Peer]

Nola Mike wrote:
> you most likely won't be as fast

Actually, it's rather the opposite -- lower octane (with no pinging) will give you more power, and hence, better MPG. Here's something from a previous discussion I had with my Ducati racing friends:

The term "Premium" is extremely misleading when it comes to gasoline. People assume that when they buy "Premium" they are buying the best there is to offer. This couldn't be further from the truth. 87 octane has more potential horsepower than 93 (or higher) octane. Octane is a rating. It is a calculation that predicts when pre-ignition will occur in any given engine. The lower the octane number the more volatile the gasoline -- by comparison, the higher the octane number the less volatile (combustible) the gasoline. Then why do racers use higher octane? Simple, the higher compression and more ignition advance an engine has, the more likely pre-ignition will occur -- hence, they need high octane fuel to prevent this from happening. If you want your engine to run the best possible, then run the LOWEST octane that you can without pre-ignition (pinging). If different terminology was used to distinguish grades of gasoline, people would think more accurately about it -- for example, instead of calling it "Regular" call it "Highest Volatility" and instead of "Premium" call it "Least Volatile".

[Brucelee]

I have run 91 with no issues.

[FrayAdjacent]

Stick with 91/93 octane. Your engine will run best on it, and get the best efficiency.

In engines with higher compression ratios, where higher octane is recommended, you can lose power and possibly damage the engine if you use lower octane fuel.

Vice versa is not really true, either. In a vehicle that runs normally on regular, you gain NOTHING by using higher octane fuel.


Higher octane ratings in fuel only increase the fuel's threshold for detonation. In high compression engines, or forced induction systems, it is necessary.


You bought a Porsche. You didn't skimp. Don't skimp on fuel.

[porsche986spyder]

Originally Posted by FrayAdjacent

Stick with 91/93 octane. Your engine will run best on it, and get the best efficiency.

In engines with higher compression ratios, where higher octane is recommended, you can lose power and possibly damage the engine if you use lower octane fuel.

Vice versa is not really true, either. In a vehicle that runs normally on regular, you gain NOTHING by using higher octane fuel.


Higher octane ratings in fuel only increase the fuel's threshold for detonation. In high compression engines, or forced induction systems, it is necessary.


You bought a Porsche. You didn't skimp. Don't skimp on fuel.

I couldn't have said it any better. You're absolutely right! For example, my last car that I had used regular gas, then I dropped a Jackson Racing Supercharger in it and I had to switch to a higher octane fuel. More oxegen per ltr. of gas burns faster and therefore runs leaner, not richer. If a car requires a leaner mixture of gasoline I would not use a richer version because if will not co-inside with the cars CPU and air/fuel ratio.

[JackG]

Originally Posted by Peer

Nola Mike wrote:
> you most likely won't be as fast

Actually, it's rather the opposite -- lower octane (with no pinging) will give you more power, and hence, better MPG.

That doesn't seem to be quite accurate.

"It is important to note that the theoretical energy content of gasoline
when burned in air is only related to the hydrogen and carbon contents.
The energy is released when the hydrogen and carbon are oxidised (burnt),
to form water and carbon dioxide. Octane rating is not fundamentally
related to the energy content, and the actual hydrocarbon and oxygenate
components used in the gasoline will determine both the energy release and
the antiknock rating."

In short, octane rating defines how fast the gas burns, and how resistant it is to pre-ignition. It does not define how much energy content the gas has, so lower octane gas can't make more power. It doesn't have any more energy to offer than higher octane gas, it can just be burned in a less-demanding environment. Running a turbo or a high compression ratio? Then you need a better-behaved fuel (a higher octane rating). Same energy content, but better manners.

[Peer]

JackG wrote:
> That doesn't seem to be quite accurate.

I'm sorry if I rain on anyone's parade -- but the lower the octane you can get away with (without pinging), the more power.

-- peer

[JackG]

Originally Posted by Peer

JackG wrote:
> That doesn't seem to be quite accurate.

I'm sorry if I rain on anyone's parade -- but the lower the octane you can get away with (without pinging), the more power.

-- peer

No rain here... the science just doesn't back you up on this. It seems you have a misconception on what "volatile" means. It is not a measurement of energy content.

You wrote "87 octane has more potential horsepower than 93 (or higher) octane." "The lower the octane number the more volatile the gasoline -- by comparison, the higher the octane number the less volatile (combustible) the gasoline."

You are asserting that the more volatile gas is, the more horsepower it can produce. That's simply incorrect. They have different burn characteristics, but the same amount of energy. Energy produces horsepower, not volatility.