it is complete custom job... as for the temperature... i have never , whatsoever , seen oil temp more than 80 deg. cel ( the normal temp that bmw give for m42 ) because the thermostat works only when the oil tries to go more than 80 , only then lets the oil go to the cooler and keeps the temp steady...even in a N/A engine , the oil must not get over 80...that is the only thing that the cooler does...there is no diference in a N/A or a turbocharged or compressor engine...
but in a turbocharged engine , the oil temp gets higher because oil is getting to the turbocharger which gets hot gas from the exhaust and may reach even 1000 deg cel in high RPM and gets very hot... so the oil returning in the engine from the turbo is cooked and looses it's abilities... if you let the oil get more temp than normal , you may have problems in piston rings , rods ech...