While I don't have the ST, the Aviator has the same engine. Also, I usually fill up with about 1/4 tank of gas left. My mileage on the last 2 fillups was 10.29 and 12.53 L/100km with about a 50/50 hwy/city split. The tank holds 76.46 L (20.2 US) which is the same as the ST.
After the last fill-up it showed 378 miles to empty.
Peter