A lot of OEM's do it and it works (alright I guess) but I've had zero experience with it. I used a external cooler and then into built in radiator cooler cause I had been reading of folks having the oil to cool. But in a friends car we just made a loop of copper tube right alongside the trans and it was in & out right back into the trans and that T400 never cared how many holeshots he did. SO maybe it is because of the tranny and perhaps known issues / failures??? Or like some of the old adages about oil in general, some is better than none!, so heat is the known killer, remove it the best you can is all I know.