After driver salary, fuel
After driver salary, fuel costs are the largest expense of operating a rig, comparable to rig cost (including financing). The rig costing 2x is breakeven, and positive return if the maintenance is lower (which it probably is). We are there already for lighter loads, and soon for all loads.
Costs:
Driver 44%. Fuel 21%. Rig 20%. Maintenance 11% (inc tires). Insurance 5%. Permits 4%
Source: sonar.frieghtwaves.com