Some of the Crude Oil from Qld was/is very Light weight & almost Diesel Like..
Trucks would Run on It, though you needed to change Filters far more often.
Not To sure how Modern High Pressure Common rail Systems would Handle the Light Crude though..
As you say Illegal as Govco missed out on the Excise.!
They were used in tipper trucks, just dumping rocks to reclaim land near Or on the Brisbane River container wharves, because they were running at very low rpm compared to highway trucks, it was not too hard on the engines, but they had to be maintained on a regular basis, as you say filters etc!