I just recently switched to T-6 as well, for my first change after buying the truck, I used Rotella T-5, 10W-30 semi-syn with two bottles of Rev-X. My engine ran amazing, injectors quieted, started better cold, and best of all after 5K miles the oil and filter looked CLEAN, the oil was still transparent, and my filter was still yellow, like new. So far the T-6 runs just as quiet, maybe quieter and smoother, and I'm not using Rev-X this time, I figure if the Rev-X did it's job, my injectors are clean, I'll use synthetic and keep them clean. BTW, I've used T-6 in my sportbikes for years, motorcycles LOVE the stuff! I dump the oil in my diesel at 5K miles, and in my bikes, 3K miles.
You must understand the prior owner used 15w-40 dino oil as recommended by Ford. When I did my EGR delete and oil cooler that oil and filter were as black as a tar patch, in fact it took a week to get the oil stain out of my hands. My opinion, the Rotella is good stuff for the money, I've seen many Blackstone oil analysis' from other forum members that confirm it. I think I won't need to continue using REV-X, I'll just wait and see this winter. But I was easily starting in the teens with no block heater after using Rev-X.
"It is true that ROTELLA T Synthetic is Group III (not PAO) based, but you must keep in mind that not all Group III base oils are created equal. ROTELLA T Synthetic is made with Shell's XHVI base oil, which unlike other Group IIIs does not begin as distilled crude oil, hence of all Group III base oils, XHVI is truly the only one that can legitimately be called "synthetic." XHVI is a wax isomerate, meaning that it is made from the slack wax removed from distilled crude in normal solvent dewaxing. This slack wax is catalytically transformed (isomerized) and hydrofinished into a chemically pure base oil which rivals PAO in virtually every category. There are other "synthetic" oils out there based on Group III, but Shell's is unique in that it uses XHVI base oil. Chevron and Petro-Canada produce Group III base oils that come close to XHVI, but even though these oils are all hydroprocessed and utilize the same type of isomerization technology employed in the making of XHVI, they are not the same thing. Only XHVI is made from pure petroleum slack wax and its CAS number is 92026-09-4. The CAS number for the more typical all-hydroprocessed Group III base oils is 64742-54-7. If you want to know what your "synthetic" oil is made from, take a look at the MSDS and look for these numbers. (The CAS number for PAO is 68037-01-4).
In brief, don't be so quick to dismiss Rotella T Synthetic as just another "synthetic pretender." It's made with the same base oil as Shell's Helix Ultra, and everytime you see Ferrari win a Formula 1 race, that's the oil in the engine."