Do diesels make financial sense?

I would like to see the actual Vicentric report. I have found discrepancies in many of their past reporting when I my company used to use their reporting for our own fleet(hence the reason why we don't use them anymore). They used the weighted average of previous months which were mainly winter months when the difference between gas and diesel is the highest. The yearly maintenance was also double what I paid annually which lead me to conclude that they did not account for the fact that the interval was twice as long as the gasoline equivalent.