Simple answer is:
1) check what the/your owners manual stipulates.
2) I checked the manual for a 2009 Ducato 250 - 160BHP 2999cc Multijet at it states:
Selenia WR PE - 5W-30 - ACEA C2 - Fiat 9.55535-S1
So technically the Shell Helix 5W-40 is the *possibly* wrong grade. (See 1) above)
3) Shell website comes up with: Helix Ultra AT-L 5W-30 for the model I looked up
There are so many Ducato models/variations/years I may have looked the wrong model up as you gave no reg.
If you find it should be a 5W-30 oil then 5W-40 is very unlikely to do any harm to your engine. 5W-40 was a common use oil for petrol and diesel engines but in later years with increased pressure on fuel economy and lower emissions 5W-30 become more used.
Point 1) above is what you should go by and follow on from there.
With regards to Selenia vs Shell vs Texaco vs Motul vs Castrol ....... then all the major well known brands are good and will exceed the required oil specification they comply and are tested to - eg. 5W-30 - ACEA C2
Fiat MultiAir and Twin Air petrol engines ARE VERY FUSSY AND DEMANDING when it comes to engine oil specification so it is always best to stick EXACTLY to the stated oil specifications.