I know lots of Porsche owners who mix 100 octane gas with their 91 (because this is the only fuel available) octane gas to net out at about 93.
No lead, and I am not sure of the alcohol content, but it is 10% max.
Most Porsche factory tuned DME's can maximize about 96-97 octane. Depending on the car (n/a or turbo), weather, and altitude, for example. Any amount about this is a waste, without a customized tune.
Is 93 "better" than 91? Yes. is 96-97 octane better than 93? Yes. Does this really matter much in street driving? Not really. But, it depends on how you drive.
