Poor MPG

There are a lot of reasons for poor fuel economy so we are going to have to start running through the basics first and we need to check codes and find out what is there.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

To start with, does the coolant temp sensor read properly or is it low or high? A faulty ECT sensor can cause this as the PCM uses engine temp to determine the fuel needed.

Also, we are going to have to inspect the operation of the o2 sensors.

https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor

Does the engine run poorly like it has a misfire? We need to use the chart below to determine if the plugs are fouled as that will cause this issue as well.

Next would be dirty injectors. If they are over fueling then that will cause a high fuel consumption but the o2 sensor info will show that the engine is running rich which will point us in this direction.

Also, if it is running poorly we will need to check for a vacuum leak.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Lastly would be a more serious issue like low compression or a transmission issue.

Did anything happen recently that would have caused this? When did it start and did anything drastic happen?