2002 Honda Accord gasmillage is too low

Is the check engine light on? Have you checked for pending codes?

With 86xxxmiles, if you have the factory oxygen sensors they are most likely pretty lazy by now. I'd give them a good look to make sure they are functioning properly.

The engine is not on. Except oxygen sendors, si there any other potential issue?
Also, do yo have any idea how much it cost if i change the oxygen sensors?

Thanks.

Well there are a few possibilities, but your PCM is pretty good at picking up faulty items within your management system. So if there are no pending codes check these items:

Have you replaced the fuel filter? Serviced the fuel injection system? You may have a small vacuum leak and or exhaust leak. And finally, make sure the o2's are functioning.

An oxygen sensor is about an hours labour plus the item. Each sensor varies so it's hard to give you an exact price on the part.