For the US, I'd recommend 93 Octane "Top Tier" gasoline (look it up). I like Shell, but interestingly when I had a gripe on my BMW E92's hard starting issues, he found the gas was 15% ethanol. Ethanol is one of the great scams perpetrated on the public. It doesn't protect the environment, it doesn't improve vehicle performance (and attacks vintage fuel systems), it delivers lower mileage. What's not to hate? Sadly, about the only non-ethanol fuel is 87 octane and not ideal for a Porsche engine.