Gas Mileage Problems Plz Help

[93 Del Sol]

Alright, as stated, I am having some gas mileage problems. I recently got a 1993 Del Sol....I dont know if it is a vtec or anything. The engine is a D16Z6....I have no idea about any of this stuff so all I know is that it has an automatic tranny and all the mileage i am getting is 240-255 miles to a tank of gas. Is this normal? If not what can I do to fix it? Thanks