We have another fillup to add to the spreadsheet. It seems the suspension work improved fuel economy? Or maybe it was just the driving conditions. But after replacing the front control arms, I also had the alignment reset. The car actually feels like it rolls easier. The old worn-out suspension bushings must have been playing havoc with the suspension geometry. This latest fillup came in at 57.5 mpg.
Also, we now have 3 fillups under the summer conditions. That should be enough data to compare against. So now it's time for some pizza pans!