Using imperial gallon measure(slightly larger than the US gallon) I get 20 in the city and 30 on the highway. 
Stamina - mine? Longest drive I have done is 4 hours to Jasper. Longer trips we take the Camry. Wife could not sit that long in the Boxster. 
Coldest temp I have driven in is about -34C(about -30F). Okay everybody flame me for doing that. 
Car gets driven regularly throughout the year . 3 years of ownership and it is certainly worth the price of admission. I would like a Cayman but don't want to spring for a CPO one. 
And you all have stamina listensing to me!
Cheers, Guy

 Have a great day.