More ignorance !
The spiderman web is courtousy of the Lubrizol corporation an American oil company since 1928 who has kindly examined the specs , without who's to tell what's what as anything can be stated on the packaging . The spiderweb shows 5W30 504.00 507.00 out performing 5W40 502.00 505.01.
As does oil specification. org , a oil manufacturer and German labritory commitioned by VW themselves who's oil spec it is who labeled the 5W40 a medium quantity oil and 5W30 high quality .
So that's four different entities confirming the same .
No doubt down to it's basestock groups and additive package concentrion as the German lab published .
The best oils like Millers CFS Nanodrive NT+ have 10-20% ester in them and the 5W30 has top group 5 ester , the 5W40 does not .
Paul's statement of don't use 5W30 in a diesel was incorrect .
Putting in the details of the gentleman's 2000-2003 8L 1.9PD 130 ASZ into the Castrol oil selector didn't even give the option of the lesser quality 5W40 505.01 !
Enter the details into the Fuchs site and..
Three 30's and one 40 grade .
Bear in mind the viscosity difference between the 30 and 40 at high temp is so close it could be considered the same ( 1 centiStoke ) unlike the 30 difference to the recent 508.00 509.00 0W20 oil is greater at 4 centiStokes .
Now I have used Castrol and Fuchs because they have been/are currently the genuine VAG oil suppliers .
I can see this old ( 1999 ) ?? 5W40 505.01 PD spec becoming obsolete as it serves no purpose as 5W30 507.00 is superior , universal , fixed / variable , with dpf / without dpf , PD / non PD .
The penny dropped for a well-known Nottingham VAG indie , he just orders the one universal 504.00 507.00 oil in 208L barrels .
5W40 502.00 505.01 will only serve to lubricate those with out of date thinking .