By the numbers (kinematic viscosity) Rotella T6 5w40 and the conventional 15w40 have basically identical numbers at 100 degrees C. 14.9 centistokes vs 15 centistokes…..
However, if you’d like to investigate how well the new 5w and 0w multi-grades protect relative to the more traditional ones….
Do some web searching and read a few threads over at the “bobistheoilguy” forums. You will find very sciency studies cited on both sides of the argument, and be totally confused and no closer to a definitive answer.
Now, back to Bill helping his friend with the original question. Did he ever get you some numbers Bill?
