I believe Shell rebranded their Rotella line of oil. Rotella T 15w40 started to be labeled as Triple Protection. They had a Rotella T Synthetic, which was the 5w40, now labeled Rotella T6.
The T5 is a synthetic blend, and I believe it is 10w30, you might be able to find a 10w40.
I believe the new "Triple Protection" rotella is designed to have less wear on the cats, which is what was harmful about the previous version.
If you are somewhere mild (climate) try the triple protection 15w40, which will help lower the knocking and ticking. If you are somewhere colder, you might need the low end viscosity of the 5w40, which is the Synthetic T6 version.
When you read around here and hear people mention using rotella, they were talking about the Rotella T, which is now Rotella Triple Protection.