Petroleum Quality Institute of America refers to the "W" as winter.
http://www.pqiamerica.com/apiserviceclass.htm
When I earned my college degree in Auto Technology many years ago, we were taught the "W" was weight. Times change is guess, and not always for the better.
__________________
149, 2072, Original, 1772, 1782, #1 cart, Parker 48" sweeper,
|