Toyota: Toyota Camry, spark plug wires, fuel air mixture

Question
We have recently bought a 1999 Toyota Camry with a 4 cylinder 1.8 engine with 122,000 miles.
The car was recently tuned and is running smoothly.  The car came with the maintenance records and was serviced regularly.
We are getting 20 to 21 miles per gallon using the least expensive regular gasoline.  I am a conservative driver and do not drive the car hard.  The mileage of 20 mpg is mostly around town.  
We spoke to a woman with the same exact car and engine and she was getting 26 mpg.
The car does not burn any oil and is runs very smoothly.
Do you have any ideas why we get such low mileage ?
Thank you
Tom Connell

Answer
Yeah, 20 is a smidge low for a '99 Camry.  Well, this sounds like a good tune-up is in order.  Spark plug wires, spark plugs, distributor cap and rotor arm, air filter check, fuel filter, PCV valve check, and 02 sensors check.

Now, what would I recommend FIRST?  The fuel filter.  It's got 122,000 miles, if it hasn't been changed, then its robbing your engine from easily getting fuel.  

The PCV valve is an easy thing to replace and costs about 5 bucks.  It's what allows the vapors that build up in the engine to get burned by it.  It's like a cycle of recycling.  If you've got a four cylinder, it should be the 5SFE and that'll put your PCV valve on the top of the engine.  It's this little black rubber line that goes from the top of the engine to the intake manifold.  I can send you a picture of mine to give you a better idea.

Next, check your spark plugs by pulling them out.  If you want, reply back so I can send you a spark plug chart for you to compare your plugs with.  The 02 sensors are also a source of gas robbing because the engine compensates for certain exhaust temperatures by changing the fuel/air mixture in the engine.  The sensors go bad over time and your engine's got a bit of mileage on it.  I can send you the info to check the sensor but you'll need a voltmeter to test it.  

I hope this helps and feel free to write back for further clarity or anything else you may need.  

-David D.

P.S. Almost forgot, two things that can also rob gas mileage include hard braking and under or over inflated tires.  Make sure they are inflated per manufacturer's instructions.  Toyota put their recommendation in the glove compartment box (if I'm not mistakened, but you can also check the door jambs or FOR SURE, it's in the owners manual.  I think it's 32 PSI though).  Oh yeah, a nice fuel injector cleaning with "Seafoam engine treament" in your gas tank will also do wonders (follow instructions on can).