Pretty cool.
I used the current national average,
AAA Fuel Gauge Report and your numbers but for a year, e.g.
premium $2.93 15 15,000 (yearly average)
diesel $2.83 22 15,000
The savings was $990/year in favor of diesel.
If I then use the numbers from 1 year ago when the diesel was more but not above $4 (couldn't find the numbers quickly but the delta looks about right from what I remember)
premium $1.84 15 15,000 (yearly average)
diesel $2.40 22 15,000
The savings dropped to $210/year
Seems like a false savings to me. That doesn't even factor in the cost of urea and the problems some are having w/the weird cold weather urea consumption.