Why does your 2001 Kia Rio use so much gas?

you havent changed any of the following :

the *air filter

*oil +filter

*gas filter

*spark plugs

*tire pressure

*the normal unlead gas you buy and don't buy fuel aditives to mix with it

* the amount of crap you keep in your car that doesnt need to be there cause your too lazy to move it

I fill my 2001 Kia Rio from empty for only 14.00 and go nearly 300 miles on that. There is definitely something wrong if you don't get wonderful gas mileage.