I never did like The Dukes of Hazzard.
However, the Wikipedia page on the General Lee is interesting.
Even if it doesn’t go into specifics about what kind of gas mileage a 1968 or 1969 Dodge Charger gets. (I have seen estimates elsewhere on the Internet ranging from 9 MPG to 11-13 MPG, so perhaps that tweet isn’t too far off. But those estimates and Wikipedia are distinguished by a notable lack of sources.)