All straight weight oils, such as SAE 30, have "Winter" weight viscosities ("W") but it's just not reported on the bottle, right? If you ran a "cold test" on your SAE 30 oil, you might have a 20W30 or 10W30. It's an xW30 where x = unknown.

Has anyone seen where the winter weight number has been reported for a straight weight oil? Just curious.

Last edited by Wally / Montana; 05/29/2025 3:53 PM.
1948 3/4-Ton 5-Window Flatbed Chevrolet

34 Years. Now with a '61 261, 848 head, Rochester Monojet carb, SM420 4-speed, 4.10 rear, dual reservoir MC, Bendix up front, 235/85R16 tires, 12-volt w/alternator, electric wipers and a modern radio in the glove box.