Sorry, yes, 5-40, oem is 5-30, so they should both (in theory) be the same thickness at cold.
I am not sure the noise isn't just the hpfp building pressure, it can't be heard from inside the car, and I have to listen for it outside, then it's intermittent and only lasts a tiny amount of time. The engine is pretty much silky smooth from then on, much quieter than most others I have heard, very quiet when warm too.