Originally Posted By: Garak
MRV is mini-rotor viscometer, which is a very useful measure for cold cranking. CCS is cold cranking simulator. There is probably information at the front page here, on the PQIA website, probably places like Afton, and the ASTM website, though the stuff won't be free at that location.
Essentially, lower numbers within a category are better for cold cranking, but those numbers refer to the temperature at question. A 0w-XX oil will be desirable if one is starting unaided in a Saskatchewan winter, but will not mean it's too thin come summer, or has better pumpability at normal starting temperatures in the summer.
To follow up - HTHS is High Temp High Shear, in other words, it's the viscosity measurement of the oil in a running motor in locations which can be considered hards on oil. Generally speaking, the higher the number the higher the film strength, higher the drag, and lower the potential for viscosity decrease. Lower the number and you've got lower film strength, lower drag, an increased probability if viscosity loss.
NOACK is the percentage of oil lost.
TBN is the Total Base Number, essentially the size and/or strength of the additive package.
These are very, very, unscientific descriptions but hopefully it's easy to understand.