I am currently driving what is called a C Train. Prime mover with a b-double towing a third or C trailer. I collect harvested grain from the farmers property (properties) and take it to a grain handling facility about 40 kms away. I drive about 5 kms on the farmers tracks, about 30 to 40 kms on a graded dirt road and 3 kms on the South Coast Highway. A round trip of between 70 and 90 kms. On each leg, from weigh bridge to weigh bridge I have been using between 50kgs and 80kgs of fuel. As diesel weighs 85kgs per 100 litres, I figure that I am getting between .8 (800 metres) and 1 km per litre of diesel.
When you consider that each load, legally loaded I weigh in at 102.50 tonne and I am around 39.50 tonne empty, I carry 63 tonne of product from the farm to the Grain Handling Facility.
Some boffin with a penchant for mathematics will/should be able to work out if this is economical or not.
Consider your own tug. Let us say that you can get 10km per litre empty and this may reduce to 7.5 per litre towing your rig. Find out the legal maximum towing weight. Let us say it is 3 tonne. At 3 tonne per load you would need to do 21 loads ( 3 into 63) to carry the same amount of product. Each trip takes about 2 hours, loading travelling, waiting, waiting, waiting, unloading, return. To do 21 return trips would take 42 hours, they are only open 11 hours a day. Every 21 trips would be about 1470 kms using your fuel at 7.5 kms per litre, you would need 196 litres to deliver 63 tonne and you would need all week to do it. Remember, the facility is open 7am to 6pm, weather permitting.
At this stage I am doing 5 trips a day, 6 on a good day, averaging 63 tonne per trip, 315 tonne delivered every day. We are just over half way through the harvest and have been going for 29 days so far.