Se saloon 2005 poor fuel average

Assalam o alaikum we just purchased corolla 2005 se saloon 1.6 a month ago. Drive and comfort is good but one thing makes us regret our decission is its fuel average. It is giving us around 5-6 KM/L max. Please tell me how to improve its fuel average. Do these model carry oxygen sensors and other sensors like map sensors or whatever. ( i watched videos they told to clean these sensors unorder to improve fuel average). Please help.