From the 2008 Ducato handbook:
"Synthetic based oils, SAE 5W-40, Fiat 9.55535, N2 qualification - Selinia WR. Should non-genuine SAE 5W-40 products be used, lubricants with minimum ACEA B4 properties are tolerated but in this event, top engine performance is not guaranteed. Using low quality products, not compliant with ACEA B4 properties and specifications could cause engine damages not covered by warranty".
So I read this as 5W-40, full or part synthetic but I think 5W-40 only comes in "full" synthetic spec. IMO, this would have done the job
http://www.eurocarparts.com/ecp/p/c...gineoils/5w40-engine-oil/?521776031&0&cc5_248
Edit - have checked what our guy put in last year and it was indeed 5W-40, sorry for the confusion.