Wow....went to that link Tinman. Looks like a major pissing contest about the subject. In the case of my truck it lived a hard life and the previous owner never said much about maintenance. My thinking was that it couldn't possibly hurt to do it at least once and I'm glad I did now. Based on the fact that it does eventually end up in the oil pan I'm thinking changing the hpop oil once a year or two isn't a bad thing but certainly not necessary at all oil changes to be sure (it's a major pain in the a$$ to do).

 

There is NO reason to do this, not one good reason to do it.

The oil in the HPO res is used and drops down to the pan as quickly as all the other oil in the truck.

 

I used the test monkey at work, a 99 flatbed waaaaay abused and found that there was NO sludgey stuff in the hpop res and the oil looked just like the stuff in the pan.

There was a post i found that the guy stated he could actually fill the whole crankcase through the hpop res givin the hole was big enough. i change mine every 5k with full syn so i am not worried any more.