A lighter weight oil is what you want. 5w30. You asked if you could run Rotella, the answer is yes, I ran it in my truck. I live in south Louisiana and it is hot here.(70+ today) It get into the high 90s in the summer, and I'm sure that was a factor in the sludge built up that happened to me. If the lifters are tapping (valve click) a thinner oil will help some (5w30) If the ring are letting oil by and then engine is burning it off then a thicker oil is needed to help stop this. I know that Havoline is good oil. As far as the synthetic oils, there are very good, LOL except Castrol, I have seen this first hand, the sludge issue again. Like I said, maybe it is because of where I live, and all the heat.
I live in houma Louisiana lol.