I have replaced spark plugs and wires and the fuel filter and mileage got worse

Check the engine coolant temperature sensor (ECT). High failure rate on these. When they go, the computer thinks the engine is colder than it really is. See the post below

Test coolant temp sensor

Check the engine coolant temperature sensor (ECT). High failure rate on these. When they go, the computer thinks the engine is colder than it really is. See the post below

Test coolant temp sensor

This link should help:

https://www.askmehelpdesk.com/cars-t...tml#post293582

Focus on cleaning the MAF Sensor and replacing the ECT Sensor. Also, replace the air filter, if it hasn't been changed in 30,000 miles. Easy jobs.