Bad fuel consumption

Hello,

Many times due to emission issues the vehicle can suffer from poor fuel economy.
Like it could have a bad oxygen sensor which can impact the air fuel ratio and can use more fuel than usual.

Did the fuel economy go down all of a sudden or has it been decreasing overtime?

Typically emission issues will trigger the check engine light. Is your check engine light illuminated?

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

The fuel economy can suffer if the driving habit changes. Like if you were to move to a area that has more hills or if you are driving more in stop and go traffic etc.

Please let me know a bit more information.
Thank you.

The RPM will not trigger poor fuel economy.
Depending on the issue with the oxygen sensor, it can make the engine run rich which can affect the fuel economy.
Let me know what is the code is for the oxygen sensor when you find out.