A mate of mines wife had one of those Disco's as her company car, used the same amount of fuel when being daily driven (she also tended to do about 300~400k's a day) so she was very happy to have a fuel card from work. They also used it to tow her horse float, and then it went out to around 30l/100k on the freeway, and more on rural roads.
With the SWB Pajero, do not tow with them, the lack of wheelbase (applies to any other SWB vehicle) makes then very susceptible to snaking and instability. My uncle had one that he used to tow a caravan from Perth to Melbourne, when he got here, the first thing he did was sell the car and get a LWB Pajero. Every time a side wind or a truck went past, the trailer started to wag the car. I have also used a SWB Landcruiser (Bundera) to tow my STi, and that too was very unstable, especially under braking.
A rule of thumb that I have been told by the guy that I bought my current trailer from is that the distance between the front wheels and tow ball on the tow car should be longer than the distance between the tow hitch and the centre line of the front and rear wheel sets on the trailer, this makes the car have a lower polar moment than the trailer, and it can then stabilise the trailers motion.