Originally Posted By: Tim H.
Cold flow, actually. I did. not include 0W weights bcs I'm getting the impression on the forum that 0W's flow about the same as 5W's at the 20-30F temps, unless I am understanding this wrong.
Not always. It depends on a variety of factors.
"Thin" can mean more than one thing, and not just because of temperature: there's actually more than one kind of viscosity. One example of how this plays out in weird ways: Mobil 1 AFE 0w-30 vs. Red Line 5w-30. The Mobil 1 is "thicker" in that it has fractionally higher kinematic viscosity numbers. But it's also "thinner" in that it has better cold pumpability numbers (0w vs. 5w) and a lower HTHS viscosity.
The point is, "thicker" and "thinner" don't really say much, which is why people resist using those terms. The best thing to do is to figure out what your goal is and go from there. Are you looking for the best possible cold pumpability? If so, look at CCS and MRV numbers. Do you want the least amount of drag in your bearings? If so, look at HTHS viscosity numbers.