Honda Repair: Honda Accord mileage problem, fuel consumption, honda accord

Question
Honda Accord 2009 V6 automatic 59k miles.  Fuel consumption sudden drop from 24mpg (mostly city) to 12mpg. No check engine light, same gas station, no brake problems, new air filter, good tire pressure. What can be the problem?

Answer
I would first have the codes checked. Even though your check engine light is not on it can still have codes stored in your computer. It would be a good idea to take your car to a repair shop to have them hook up a good scan tool to it so they can look at the datastream, this will help them see what might be going on.
I'm assuming you've re checked your math a couple times! That is a huge mileage drop. I'd start with having the codes check and checking the data stream. Without some type of hint as to what is going on you will be just stabbing in the dark.