Mild 318 pinging

So you don't run vacuum advance at all? I've always been told that no vacuum advance will kill your mileage but I've never tried it myself. Of course, I know not everyone is concerned about fuel mileage when it's just their "toy" car. I didn't worry much about it when gas was in the 2's.
It puts a dent in mileage for sure. They all react a little different though. Some are affected more than others.