[cobrin]

Step 1. Finds someone proficient with ODB2 scanners and get them to look into the coil packs or ignition issues, any miss fire is wasted fuel, and another cylinder/s might have to increase their duty cycle to keep up. I would be replacing the coils if any are found faulty. $100ea isn't kind on the wallet. Hot and cold, so the tester you find will want to be smart.



Step 2. Have the injectors tested and cleaned. Obvious reasons on this.


Step 3. How many K's on the engine and when was the last sparkplug change done. If you've had a rough idle it may help the solve the issue, or at least point you into the right direction.



Spitballing: Have you had your transmission serviced lately? an over filled trans (one that is higher than full, but not high enough to give show stopping results) can create a drag on the driveline and increase fuel consumption.