what would make a 4 cylinder car burn over half a tank of gas in less than a day?

[Hatchet Warrior 69]

i put 20 dollars in gas in my volkswagen jetta 3 gl an it gives me half a tank of gas and within a few hours of drivin im on empty agin an havent went that far at all what could be causein this an how do i fix it to get better gas millage?

 

[john926]

i have a 4cyl civic ex and one of my cylinders froze up make my car run very very awful. i wud push all the way down on the gas and barely go over 35mph. id suggest taking it to your local mechanic to have it checked out befor it leads to worse, more expensive problems.