Oil Rating

[Eugene Balinski <eugeneb@nni.com>]

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