2003 Jaguar X-Type TOO MUCH PETROL

HI,CAN YOU TELL ME PLEASE WHAT I CAN DO IF MY CAR TAKE TOO MUCH PETROL.ITS 2.0 PETROL WITH MANUAL GEARBOX.I CAN DRIVE JUST 40 MILES WITH 11 LITRES OF PETROL.i heard about engine tuning,can this tuning help to solve this problem????THANK YOU