I run rotella T full synthetic... I change it based on time not miles... I just change my oil every summer, I usually put 15-18k on it each year... Every time I have changed it... the dang oil is still somewhat clear looking...
The rotella T is a diesel oil designed for sustained high temperature.... It does scare me at low temperatures so I typically take it easy on cold oil temps, and get a very light 5w-40 viscosity.
Another cool thing with this rotella was my blown headgasket on my fiero this season... I dumped 2 quarts of coolant into my oil pan and drove around for probably 40 miles... flushed out the water, put more rotella back in, good as new!
