Straight from the ASTM website:
Quote:
CCS apparent viscosity is not suitable for predicting low temperature flow to the engine oil pump and oil distribution system.
Quote:
A correlation was established in a low temperature engine performance study between light duty engine startability and CCS measured apparent viscosity. This study used ten 1990s engines at temperatures ranging from –5 °C down to –40 °C with six commercial engine oils (SAE 0W, 5W, 10W, 15W, 20W, and 25W).8
It is a rough estimation for the cold engine startability. CCV should by no means be used as the basis for cold oil performance, it is written right in the spec. Why? Only the apparatus is cooled down to the reference temperature. Then the oil is poured in and the test begins after 90 seconds.
Now lets see what the MRV test has to offer:
Quote:
When an engine oil is cooled, the rate and duration of cooling can affect its yield stress and viscosity. In this laboratory test, a fresh engine oil is slowly cooled through a temperature range where wax crystallization is known to occur, followed by relatively rapid cooling to the final test temperature.
Quote:
These laboratory test results have predicted as failures the known engine oils that have failed in the field because of lack of oil pumpability
Now, this is a much better test to represent true cold starting conditions. The oil is actually cooled down for over 45 hours to ensure the oil properly reacts to the low temperature. Not only that, the test was clearly developed to deal with engine failures due to the inability of the oil to be pumped.
Quote:
CCS apparent viscosity is not suitable for predicting low temperature flow to the engine oil pump and oil distribution system.
Quote:
A correlation was established in a low temperature engine performance study between light duty engine startability and CCS measured apparent viscosity. This study used ten 1990s engines at temperatures ranging from –5 °C down to –40 °C with six commercial engine oils (SAE 0W, 5W, 10W, 15W, 20W, and 25W).8
It is a rough estimation for the cold engine startability. CCV should by no means be used as the basis for cold oil performance, it is written right in the spec. Why? Only the apparatus is cooled down to the reference temperature. Then the oil is poured in and the test begins after 90 seconds.
Now lets see what the MRV test has to offer:
Quote:
When an engine oil is cooled, the rate and duration of cooling can affect its yield stress and viscosity. In this laboratory test, a fresh engine oil is slowly cooled through a temperature range where wax crystallization is known to occur, followed by relatively rapid cooling to the final test temperature.
Quote:
These laboratory test results have predicted as failures the known engine oils that have failed in the field because of lack of oil pumpability
Now, this is a much better test to represent true cold starting conditions. The oil is actually cooled down for over 45 hours to ensure the oil properly reacts to the low temperature. Not only that, the test was clearly developed to deal with engine failures due to the inability of the oil to be pumped.