65 Barracuda daily driver

Also, did I just get 21.56 MPG with a small block??? Previously I had gotten maybe 13 mpg tops. I started taking photos of the pump and the odometer every time I put gas in the car, or did I forget one? Seriously confused. Even the slant 6 before only got 16-18 mpg. Could it be that that last metering rod change had such an impact? I have to keep an eye on that