MPG calc?
 

Up here we use litres and my odometer is in MPH...so help me out.

Give me a factor. How many gallons in an SC tank?

How many miles on a tank should I get on mixed city driving and what does that equate to in MPG

Multiply number of liters time 3.785 to get gallons. A typical 911 has about 21 gallons so it should hold 79.49 liters, or so. If you get like me about 18 miles per gallon, then you should get about 378 miles, but you wouldn't want to go much over 300 miles.

The power output in my British piece of trash is measured in stone-furlongs per fortnight, not horsepower.