Generally I hear to run 15-40 and always have. But I was reading my manual and it recommended 2 oils, 15-40 and 30w.
It gives a scale for each oil. Seems like they only recommend 30w for temps above zero degress and 15-40 for sub zero temps.
Living in CA I've never seen subzero temps. Ocassionally (rarely) we get in the high 20's.
So, I'm wondering if there is benefit to running 30W?
For the record I run Rotella 15-40 - my local auto parts store carries Rotella 30W.
The reason I ask is - My engine runs quieter and smoother when I first change the oil (about the first 500 miles). I can actually hear it quiet down about 5 seconds after I start it after changing the oil. I'm thinking 30 is thicker and may prolong that? Or not?