I run my 2.8TD 93 Pajero (Shogun in a kimono) on 60/40 diesel/veg oil mix and it's fine.
I buy my veg oil from Tesco (KTC veg oil 15L drums at £8.20- roughly 52p a litre or so) and add .75 litre white spirit and leave to react for 5 days. This thins the veg oil to only 6% thicker than diesel fuel so no modifications required at all, and it might even run in the TD4. Investigate further before doing so though. The Paj 2.8TDs are a bit fickle. Some run happily on 50/50 mix, some prefer 70/30 (without thinning). You have to suck it and see.. I don't always thin the veg oil with white spirit and it runs just fine. Starts smoother with thinned oil though.I usually give it a couple of glow plug clickes before firing up.
Check out this section for further Pajero/Shogun veg oil advise:
http://www.pocuk.com/forums/viewforum.php?f=77
From what I remember, someone on another forum with the equipment tested the viscosity of veg oil and found it about 260% thicker than diesel, but only about 25% thicker when mixed with diesel, and 6% when thinnned with white spirits. This is a chemcial reaction that takes about 4-5 days to complete, then add to tank. White spirit does not harm the engine, although 'technically' you would be modifying the veg oil and so should pay duty on the oil used... It's interesting to note that white spirit supposedly does not contain fuel markers though.
After running a few tankfuls of veg oil mix, you should replace the fuel filter as the veg oil cleans out the tank and lines and so fills the filter with crud depending on how dirty the lines/tank was.