The hydraulic lifters, which are also used in some of Ford's Zetec engines created a lot of trouble with 10w40, which was the reason why the 5w30 was developed or otherwise known as Selenia Performer. The 5w40 was not only replacing it but also covering a wider range of applications, which is the reason why they called it the WR (=wide range).
The hydraulic lifters are astill the same and a lot of the real Fiat technuicians will tell you to ignore what the hand book says and will advise for the WR rather than the 20k.
And just to stop the argument: I have no finacial interest in Selenia WR!