Okay...if you are getting gas mileage that low, you are either not computing it right, or something is wrong with your motor maintenance wise. What mods do you have on your car?
Do a quick cheap tune up and see if this helps.
#1. new clean air filter. If you have a CAI, clean your air filter per the manufacturers instructions
#2. New spark plugs. Replace your plugs if they are older than 20,000 miles. Try NGK "V-Power Coppers". If you plugs are fairly new, pull them off and look at them. Report how they look here. Whiteish/grey ash deposits mean oil is being burned...black carbon means you are running rich. If possilble, report on Each cylinder seperatly.
#3 If you have more than 25000 miles on your car, change out your fuel filter.
#4. Check your coil pack for "arcing". Park somewhere in the dark as far away from any light source as possible, Then Rev the engine by moving the TB. Do you see sparks from the spark plug wires or coilpack? If so, consider replaceing them.
#5. Over 60,000 miles, replace your timing belt.
#6. Over 100,000 miles, replace BOTH o2 sensors.
Leave it to Random to Needlessly complicate things.