My car Hyundai Elantra 2001 1.6 engine fuel consumed abnormally on 2001 Hyundai Elantra

My car Hyundai Elantra 2001 1.6 engine fuel consumed abnormally you examined the car on a test does not show any problems in sensors and systems functioning normally I do not know what to do to solve this problem

2 answers
when was the last time you had a tune up?
What is long and short term fuel trim readings?