I'm pretty sure you have the old 2.5 shogun/Pajero lump in there, in which case you should be easily able to run at 50/50 diesel/oil mix, maybe less oil in the winter if you find starting a bit rough. You can think the veg oil for 4 days or so with 10% petrol if it makes you happier.
Have a look on the link I posted above.
Bear in mind that veg oil is thicker and has a habit of cl;eanig the tank out so the fuel filter will need changing after a tank or two..
