dont be confused Bloodyaussie,
I think there are several thoughts going around about these, although not quite on the same page, they are valid points to consider

the oil cooler is just that
an extra "radiator" to help dissipate the heat generated by the engine for the oil..............

pretty much the same as years ago, you used to fit an "aftermarket" transmission cooler to help the Auto box dissipate the heat generated in there
pretty much mainly for towing, as the Auto does more work.

now the ONLY problems I can see (with my limited future vision) is where do you mount the damn thing

common place to mount would be behind the grill - so its in front of the current air con and engine Rads......
- this would slow the air down more in trying to cool your water - dont think its a good idea myself

mount it on top of the motor (like an intercooler) have a scoop - only spot is on the passenger side
- right above your Turbo (which is generating heaps of heat - heat rises - oil cooler useless)

under the roo bar at the front, under your winch
- maybe stake it or get crap in it - or block the bottom of the engine / aircon rads..........

mount it on top of your roof rack
- looks like crap and everyone will think you secretly want a comp truck

inside one of the guards - (like the Mini Radiator)
- mmmmm room V's actual efficiency

throw this one in there as well......

in front of the Passenger side windscreen - dont think the Boss, or the Police would appreciate that one.....

was speaking to a couple of mates who plays with Turbos etc... and have been playing with this for awhile
1. the cooling system on the 4.2 is crap
2. the oil cooler at best will only lower the engine temps by about 1* - depending on where it is situated
3. Factory or Nissan Water pump (after market impellers are smaller than OEM
4. factory or Nissan Viscus Fan hub - aftermarket dont last
5. Jury is still out on the Thermostat Nissan V's aftermarket

have been told that testing - temp probe at water into Rad and water out of Rad - only 5* to 6* difference
thats with temp probe at Thermostat and temp probe (drilled and tapped) into near water pump showing close to 100*

hope this helps you mate............