Sudden MPG Reduction

[geneowens]

My MPGs have over the last 6 weeks gone from 27/28 to 23/24. My driving has not changed. I had the dealer replace air filter, and tranny fluid. I made sure tires are aired to 36 psi. Any other thoughts or recommendations? Mine is 06 Sienna CE.
Thanks,

[08SalsaMax]

27/28 seems like a lot to start-out with. I could be the ECU getting used to your driving habits, gas, altitude, or anything else.