We kindly ask you to inform us if you can use our Greek licence driving car or we need another type of driving licence in order to drive a car we rent from sixt, Thank you in advance

In California State any drive licence European is valid , but it is highly recommended to take the international driver's license, as a translation for the authority, and so you can go 100% sure

I recommend to play safe and take international license . Be sure that it matches with your name in Passport.Also do bring a credit card for rental as they don't hold temporary deposit on debit cards. Safe travels to you guys.

I agree with Luís Canelo for 1 simple reason: how would them know that your document is a Drive License?!? Even the alphabet is much different. If you wanna play safe, ask for an Internacional Drive License. Here in Brasil, I got it in 5 days, with all Burocracy that we have.

European drivers licenses should be enough, as long as you are older than 21. Make sure that you bring the same credit card as used to reserve the car. Best to contact SIXT directly beforehand.