The SAE has caused a lot of confusion by not adding a letter suffix to the viscosity grade number for the high temperature (100 and 150 degrees C) oils. I can't provide a link to the official SAE J300 specification, but the "SAE Viscosity" table in the
Synlube link seems to be fairly complete. (Scroll down a frame and click on "SAE Viscosity"). Most of the notes have been left off, but the temperatures are degrees C, the kinematic viscosity is in centistokes, and the absolute viscosity is in centipoises (I think); mo more Saybolt Universal Seconds!
Note that the cold temperature grades (W) are 0W, 5W, 10W, 15W, 20W, and 25W. The high temperature grades are 20, 30, 40, 50, and 60. Thus, the only grade that can have the same number on both sides of the hyphen is 20W-20. When I srarted working in a filling station in the mid-fifties, we sold a 10W, a 30W, a 20W-20, and a 10W-30. When a customer asked for "a straight 20 weight" we sold him a 20W-20.
Autozone just mislabeled the Kendal Oil in the ad that Tim linked to; the
Conoco-Phillips-Kendal website uses the appropriate SAE "W" and "non-W" grade designations.
The
1953 Chevy Truck Owner's Manual does not seem to be advising any oil with a higher viscosity than 20W-20. I would not want to use a 50 grade oil, especially in a cool climate.
Hoyt
