Check tire pressure and see if parking brake is fully releasing. The drag from low tire pressure effects MPG. Honda recommends (to me) are too low. I do 36 in all tires and saw 2 MPG improvement.
A friends Ridgeline was only getting 15 MPG - tire pressure was 35. Took to dealer and found that the parking brake was not fully releasing and was lightly dragging. After they repaired the cable in the wheel, the MPG increased by 5 MPG.
On a flat surface in Neutral, you should be able to push your Ridgeline. If it takes too much effort, it may be dragging parking brake(s).
My 2 cents.