Looking at oil with the naked eye doesn't tell much of anything. If you really want to know, get it analyzed.
Unless there's a problem with the engine, the RP you're running is fine. Rotella would be a downgrade.
Read this: Puts all the zddp bs to rest.
ZDDP:
http://speedtalk.com/forum/viewtopic.php?f=1&t=31791
Diesel oil:
http://speedtalk.com/forum/viewtopic.php?f=1&t=32279