the economy of running one
If you read into it, they have made at least one of the following bad decisions:
1. no vacuum spark
2. plugged/removed the primary power valve
3. too numerically high axle (4.11:1, etc.)
4. Holley 750
5. stall speed high enough that the converter is slipping at cruising speed
6. bad automatic choke adjustment
Obviously, some of it is high weight, large frontal area, driving style, prolonged idling ("to warm it up"... with the choke on)
