2001 Hyundai Elantra Q&A

2001 Hyundai Elantra Question: My car Hyundai Elantra 2001 1.6 engine fuel consumed abnormally

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 -
Answer 1
when was the last time you had a tune up? -
Answer 2
What is long and short term fuel trim readings? -