Someone else explained it that way recently, but I don't think that is
quite correct. It seems to defy the laws of physics. The measured
viscosity (of a single weight of oil) would generally get higher when
cold, and lower when warm, all else being even. I suspect it means
something more like "when cold, flows no worse than 20w (light oil) at
that temperature; when warm, offers the same lubricating qualities as 50w
(heavy oil) at that temperature". In other words, it doesn't "change"
from one viscosity to the other -- it is referring to two different
properties: one associated with low viscosity numbers (flow), and one
associated with high viscosity numbers (protection against wear). How it
manages that, I don't know.
Or maybe I just have no idea what I'm talking about...
Eugene Balinski had this to say:
>Could someone please remind me about motor oil
>ratings ? In particular, what is the "W" for in
>20W50 ? As I remember, it means that the oil is
>20 weight in the Winter (or cold wx), and 50 weight
>when warm, gradually changing from one to the
>other. In this manner, it flows more easily when
>it is cold. Is this correct ?
>
>Thanks,
>
> Gene
>
> 80 B
>
>
--
Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the red one with the silver bootlid.
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