Can off road diesel be used in an unlicensed dump truck?

Yes but off road diesel is usually highsulfur and may cause you some injector problems over time. Very hard to find but look for low sulfur off road. The only physical deference between low sulfur off road and low sulfur on road is a die that is put in the fuel causing it to be red and more easily detected when checking fuel for tax evasions purposes because you don't pay hwy tax on off road fuels.