This thread includes a thread started by chrisXJ which we had merged to keep similiar info together and save some search time.
In addition to the info posted in this thread .... there is also a collection of threadlinks a few posts further down.
As there is lots of thoughts on whys, why nots, sizes, line routing, bypassing stuff, cooler before heater, cooler after heater etc etc .....
How about a collection of info in the one thread including links to past threads and posts on oil coolers.
I'll start with this ......
The red and blue colours denote coolant temps,
The long thin pipes are the tranny line connections.