For some reason (not just picking on you) everyone has this thing for "per tank". 350km = 217.5mi, if a full tank is 16 gallons then you are getting 13.6 miles per gallon. That is horrible even in really cold weather. Unless you let your car warm up for 15 minutes before you drive, there is something wrong. My Crown Vic gets 18 mpg at it's worst.

Maybe you should double check.

"Those who cannot remember the past are condemned to repeat it" -George Santayana