2000 V6 ford mustang bad gas mileage?

So my Ford Mustang its eating away gas kinda fast for my understanding, i do around 6.5 miles to work and the same back to the house but for some reason its going kind of fast. To put it into perspective i filled up my tank last night and it has gone through a quarter of the tank in less than a day, my calculations is that it'll be by half of tank tomorrow. So for those car experts out there can you give me a suggestion about what could the problem be?

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