I went back and forth for quite some time between the Oilgaurd and the FS 5000 (whatever it is) and just couldn't get past the return in the drain plug. The Oilguard return is to the oil filler tube and that is what convinced me.
Very nice kit, well put together. Easy install. I mean it, you're just taking off your oil filter cover and filler tube cover, drilling a couple of mounting holes and running some hose. Easy.
In college I worked at an automotive/truck parts warehouse and was convinced then about the wisdom of additional (bypass) filtration of the lube oil and coolant and pre-heating the fuel. All are good things to do for a diesel.