I'm surprised at that 13-16 figure and it begs the question, couldn't a manual transmission equipped R1 Avanti fare better?
I have an example to share. Three Avantis left the SF Bay Area headed to Seattle for the 1992 regional meet. I was supposed to go also, though with split parents my mother vetoed the trip for 14-year old moi.
The three cars were a family friend's R2 4-speed, 1025 (R3 auto), and an R2 auto. My uncle Doug thought for awhile before 1025's poor fuel economy was due to Ron being heavy footed. The truth came out during that journey though. I heard all three would fill up, then only 1025. Repeat as necessary over the 1600 miles there and back. If I'm recalling correctly, 1025 was getting no better than 9 MPG, even at steady highway speeds. Actually, the new owner of 1025 has a fuel records booklet left in the center console. I kept track of gallons in, miles traveled, and cost while it was my daily.
I am very tempted to pay for A2 wind tunnel time (once I reach the appropriate phase) and test my build to discover where I should place my desired body tweaks: louvers, vents, inlets, and otherwise. I must pay for a minimum of 2 hours anyway and speculate my findings could be complete in 45 minutes. If other SDC / AOAI members were to meet there, with the remaining time we could finally get Cd numbers for four or five other Studebaker and/or Avanti cars: a '55 Speedster, a Studebaker Avanti, a stock Blake Avanti, and the 1990 sedan.