I have a 2005 EX-L. We bought it with 70k miles on it about 2 years ago. Currently it has approx. 120k miles. Easily for the first year and a half we owned the van we had no problems with the gas mileage. Our mileage was quite consistently 18-19 MPG local and 23-25 MPG highway. For the past few months it has been getting continually worse to the point it now gets 15-16 MPG local and barely 20 MPG on 100% highway driving. There has been no change in our style driving either.
Things to note:
-Plugs replaced @105k along with TB and Water Pump.
-Replaced tires ~10k miles ago with the same exact tire it's had since 70k miles.
-Aligned when new tires were installed.
-Fluids regularly changed.
-Air filter is new.
-I just replaced both primary O2 sensors with no signs of improvement.
-I also increased the tire pressue to slightly above the recommended pressure, again with no improvement.
-I removed and cleaned/inspected the EGR and PCV valves. Neither showed any indication of any buildup.
-I also pulled the plugs and they looked to have the wear you would expect. (Neither rich nor lean)
-The only qualitative things I can note are the engine seems to feel and sound slightly rougher than it used to. Also, the exhaust has a stronger odor than what I recall previously, although it is nothing like the sulfer smell I'm used to associating with a bad cat.
If anyone has suggestions or experience with a similar issue, please respond.