The average is ok and it will increse as you drive more miles. Mine is giving now 12.5 - 13.25 in city, mileage 14,375 kms. 13.25 I got after filled regular from Byco and 1/3 Hi-octane from Shell.
In my experience Shell Unleaded gives great mileage on this model.
Dry dusting is the main cause of swirls. Even a wet cloth would cause swirls. Always use a waterless wash spray and wipe off the dust with a microfiber cloth panel by panel.
Wash with a good shampoo in one bucket and clean water in other bucket and wash panel by panel by constantly dipping and cleaning the wash mitt or microfiber towel in clean water bucket.
Get a good quality wax (not polish) and apply it once a month after washing the car. I hope it helps.