this could be caused by,
dragging brakes
low tire pressure,
dirty fuel filter
dirty air filter
wrong viscosity oil
and last but not least
A HEAVY FOOT ON THE GAS PEDAL
Bad coolant Temp sensor
Bad gas mileage can sometimes be attributed to a vehicle in need of a tune-up. Have your car serviced and see if that improves the gas mileage.
bad gas mileage
Yes
Could be lots of things. How bad is bad? Should be getting 15+
hummers
yes
Yes it can reduce gas mileage. There are usually two kinds of faults with FPR that reduce gas mileage. 1. Excessive fuel pressure. 2. Fuel leaking through vacum. Both these faults result in bad gas mileage.
bad
no
Yes it certainly could cause bad gas mileage especially if it is plugged up or if your car's oxygen sensors readings are faulty.
sounds to me like it has a bad vacuum leak, check around the intake for hissing sounds
YES YESYESYESYESYESYESYES