Yup, which is why when I blend I actually shoot for something around 95 to give a margin for error. But outside of the exceptional situation, if Porsche's own specs are to be believed, the car is tuned for max performance with 93....

On that I have no doubt. I and a friend of mine took his CGT and put racing fuel in it (I believe 120 octane) and the performance of the car was essentially the same. We tried different measuring techniques and the performance gain was negligible.

Higher octane than what is recommended only causes carbon buildup in engine.

This is way wrong. Any modern car with EFI and O2 sensors will adjust properly to ethanol. Going from summer to winter has a larger difference in your fuel trims than a small mix of ethanol will have.

Ethanol is going to resist knock better, run cooler, and is just better overall for performance applications. Just look around at the power made with ethanol. Even cars not tuned for a specific ethanol mix will benefit. As long as you are below a 20-30% mix any car made in the last decade will be fine. Your car will add the extra fuel without your input, the extra O2 in the ethanol will add power and the cooling from both the flame and the extra fuel will resist detonation.

Biggest issue one could run into is running out of fueling capacity in very cold weather with a DI engine. Port injection engines will likely have plenty of headroom to avoid any issues.

To add:
I am not sure why any performance guy would be for non-leaded non-ethanol gasonline. Removing lead from fuel helped bring the demise of the awesome high compression big block engines since straight gasoline has terrible pre detonation issues. Ethanol is the best thing we have (due to EPA) to improve gasoline "cleanly". Gasoline with no additives is probably the worst thing when it comes to high performance.

Without spending the effort to go through all these points, I'm just going to suggest you study the issue a bit more, if this is an important issue for you. I think you have made some assumptions that do not hold water.

If you think a 30% mix of Ethanol is going to produce more power than an identical normally aspirated engine running pure gasoline (and the octane is what the manufacturer specifies), I think you are going to be in for a shock if you take the car to the dyno, even if you happen to be using a "Flex Fuel" vehicle that can adjust mixture to maximize power for each fuel.

Also, if you have a catalytic converter, I'd suggest you stay away from lead...

I can't tell from the photo in your avatar, but I am hoping your 944 is a Turbo (951) or TurboS, otherwise this talk of Ethanol is really off-base. If properly tuned, Ethanol can make big power in a turbocharged car (with additional boost and enrichened fuel mixture). I've already stated that. If your 944 is naturally aspirated, ethanol is a horrible idea (particularly given the low compression of those motors, especially early US models, 9.5:1).

I have tuned my own car(not a canned tune, legit tuned my own car) for ethanol and have studied over and over again before doing so. This is not with my 944T which is long gone now.

Most NA cars even will be tuned to lean out the AFR's and increase timing. 93 or 91 for that matter is not the same through out the country or during the year, and ethanol helps boost the crappy gas that most places have. In ideal conditions having the exact fuel was tuned on sure... but in practice you will never be dead on, otherwise cars wouldn't need to have any closed loop systems. and in these cases ethanol will help.

I never said to use leaded gas with cat's....? Cat's were the reason they forced non-leaded gas and brought along with it restricted, low compression engines to avoid detonation that you will see from pure gasoline.

All a flex fuel vehicle does is adjust a fuel scalarwith an ethanol monitor to keep your trims from going haywire.

I assume your car is turbocharged? If so, I'm on board. My Evo loves E85...

I would never put any amount of Ethanol in my 73 911 or a new GT3 though, if I could avoid it...

As a fuel wholesaler with a small retail outlet to the public we carry 93 octane non-ethanol fuel as a niche product. All modern cars will run just fine on E-10 blended fuels, however without being scientific you will get better fuel mileage with non ethanol fuel, typically 2-5 mpg depending on your vehicle. We have a heavy muscle car customer base and they seem to gain the most mpg while more modern cars are at the lower end of the mpg improvement. Lots of engineer types in our neighborhood. Some have even brought in excel spreadsheets documenting their better mpg figures. I can tell you personally that in my 2012 F-150, towing my track car, that I have seen a 2.7 mpg improvement versus E-10 fuel on a 300 mile road trip. An additional advantage of non ethanol fuel can be realized if you let your car sit for extended periods of time due to the water absorbing characteristics of ethanol and it's propensity to phase separate.

Thanks. The reason that you and your customers experience the improved fuel mileage is because non-ethanol has more energy per unit of volume and also means the car should be more powerful and faster when using it too.

Exactly.

Not sure why mpg's are the target result with fuel when we are talji g about Porsches but whatever.

There is so much more that goes into making power than energy density that it means nothing in terms of performance.

Not sure why there is such a love for pure gasoline when it is an abysmal fuel in terms of performance. This is why no racing entities have EVER used regular fuel. Anything is better. Gasonlines advantages come with ease of starting and lubrication. Back I. The day these were important for your typical car. Modern systems do not need these requirements but gas already has the infrastructure in place.

I personally wouldn't touch additive free gasoline with a 10 ft pole and NEVER would use it for anything I needed or wanted performance from

You still haven't answered my question about whether your car is turbocharged. If so, fine. If not, ethanol is going to rob performance and this is a GT3 board...