What mileage does your slant six powered ride get?

I get in the area of 24 miles to the gallon in my stockish 71 valiant 4 door. I say stockish, because it's got a pertronix ignitor.

The way I measured is by knowing a fixed distance between two points (not city driving), and filling my tank up immediately at the beginning and end of the trip. So I know I'm 100% full when I start, and I know exactly how much fuel it takes to make me full again (spilling out the fill hole).

It's consistent too. I've done it multiple times. I kept receipts while doing it. None of it relies on the speedo, odometer, or fuel gauge.