Couple of issues.
For just figures
Say for illustration.....1.30 per mile and .45 FSC. We have had .70, 72, 62, 49, 38, for this week.
1.30 at 40 percent = .52 per mile
Same scenario at 60/40 +FSC = .78 +.45FSC=1.23
On a 1000 mile run, one makes 520
The other on a 60/40 makes 1230 but...