A Mass air flow sensor cleaning is probably a good idea. Dirt can build up on the senor giving a false voltage reading to the engine computer, with this false reading the computer gives the incorrect amount of fuel to the engine.
I'm going to provide a list of what I think should be inspected.
Air pressure in tires( I'm sure you or mechanic check this) -can cause increased rolling resistance, there for needing more fuel to push the car
Tire alignment- -can cause increased rolling resistance, there for needing more fuel to push the car.
Sticking brake caliper components- acts as if brakes are slightly applied, also causes extra force to move car forward.
Partially clogging catalytic converters- not enough to set a check engine light, but work the same as a dirty air filter, as an air filter can restrict air flow into the engine the catalytic converters can restrict air out of the engine.
Wheel bearing wear- although usually accompanied by a noise, wheel bearing were can also cause the car to no free wheel as easily causing more force to move the vehicle.
Fuel injectors and carbon build up on intake valves- over time fuel injectors can not provide a less then optimal spray of fuel resulting in less atomization of the fuel, this can also occur with carbon build up on the valves, they act as a sponge so less fuel gets into the engine properly atomized.
These are just the top items that I would start with, If you want to discuss these further, or more elaboration on these please let me know and I would be more then happy to help.