Multiweight oils and polymers explained
W means that an oil has been designated as suitable for winter use by the SAE
Example 10W-40
The first number (in this case the 10) describes it's viscosity when cold
The second number represents it's warm viscosity
But I do agree that the further you spread the weights the worse it is for the car under load once warm due to the higher concentration of polymers. At the same time a lower cold weight helps save your started by reducing the work it must do in pumping the cold oil.