I did what you said, I pulled up the Rotella website and emailed their technical department. I told them exactly what I had done and asked for their recommendation as to whether to drain the tractor and start again. I got an answer in a matter of hours. I was impressed. Those guys at Shell are really responsive.
Suffice to say that I don't think they were too impressed with what I had done but in short here is their reply.
<font color="blue"> </font><font color="blue" class="small">( While I do not recommend mixing two separate oils, there are no compatibility issues that would warrant draining the oil before your next scheduled change.
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So I guess I'm off the hook but I don't think I'll be doing that again. No more mixing for me. Thanks to you guys for pointing out the potential problem. Lets get back to the either/or discussion before I start felling stupid again.
I think I'm leaning towards using the Rotella Synthetic in the tractor from now on, after all, it's just a little over 3 quarts and continueing to use Rotella T in the truck.