Short journeys you could say a 0W30 507.00 Shell Helix Ultra Professional , big difference in low temp viscosity compared to 5W , with 5W it takes longer to thin , with 0W you have less drag straight away and able to achieve more mpg during warm up or short journeys .
Sam .
VW 5W40 diesel oil top spec is 505.01 which is a group 3 oil basestock with a high dose of anti wear metals in it's additive package .
The high dose is there to protect the narrow valve cam lobes of a PD camshaft , they are narrow and thus more vulnerable to wear . Narrow because a 3rd middle lobe is used to drive the PD unit injector .
Now these anti wear metals burn leaving high ash that would eventually block a DPF.
To get around this they set about making a low saps oil that would also supersede the old LongLife spec 0W30 506.01 .
507.00 was born and out performed every VW spec oil before it . The performance comes from the addition of higher oil basestocks 4 and 5 so it becomes a more complete oil with 3 , 4 and 5.
4 improves the broad range of temperatures.
5 ( Ester ) takes more high temp abuse and superior detergency .
3 , 4 and 5 is used in Ester marketed racing oils !
Along with a higher overall additive package concentration makes 507.00 a high quality LongLife oil .
Now with the viscosity , an oil is graded according to its thickness / ability to flow at 100°C , each grade has a range of about 4 units of viscosity - Centistokes . So you can get thick and thin 30's and 40's .
According to Castol Edge and Quantum data sheets...
5W40 505.01
Castrol Edge and Quantum Platinum
is 13 .
5W30 507.00
Castrol Edge and Quantum-Longlife III
is 12 .
So 505.01 is a thin 40 grade and
507.00 a thick 30 grade , just not enough difference .
So the 5W30 507.00 is higher quality and almost the same grade as 5W40 505.01.
It's all about oil basestock groups and the additive package that gives it's quality .
bamboozled. 
