From a 76 Lubes publication:
"New Cold Cranking Simulator (CCS) viscosity limits for multigrade engine oils, part of
the SAE J300 Engine Oil Viscosity Classification standard, were established back in December 1999. Although not specifically part of API SL/ILSAC GF-3, these new limits are included here because mandatory compliance begins June 2001, and thus applies to all multigrade API SL/ILSAC GF-3 engine oils. The new CCS viscosities are measured at a temperature 5°C lower than previously, and the maximum viscosity limits are essentially
doubled. The reason for this change is that modern passenger car engines start at lower
temperatures and with higher viscosity oils than the engines used to establish the previous
...Except now GM wants to go back to the old Cold Crank Simulator limits.
Not quite. The latest J300 CCS spec is a slight relaxation of cold-cranking standards. Lowering the temp 5*C increases the cranking viscosity of the oil about 1.6 to 1.8 times (depending on the oil and the temp). So they reduced the temperature of the test 5*C and doubled the allowable dynamic viscosity.
The cold pumping test was unchanged. This website goes into a little more detail about the changes:
[ January 02, 2003, 03:05 PM: Message edited by: Jay ]