i run an oil cooler but its the stock 7mgte oil cooler, i plan on installing a bigger one later. as for aftermarket, ,do not run it in parrallel, that will allow unfiltered oil to get to your bearings. personally id put it after the filter so you wont have to worry about any contaminants haveing the chance to clog it even though that is unlikely. but if you put it in line with the filter make sure it will flow enough volume. and try to get an oil cooler with threaded fittings. if it has hoses just clamped to it the pressure could cause them to pop off which would really suck.