Just been struggling to get the right engine oil for my 1986 diesel. Eventually found a company called Morris lubricants – their technical team can be reached at 01743 232200 and they can recommend the right product for those of us who have older engines. Good service and free delivery. Website is at :
We had a long debate on some national (e.g. French) forum http://www.plaisance-pratique.com/huile-pour-moteurs-diesels#forum20865 and came to the conclusion that oil o use with old engine has to stick to API SFCD 20W40 norm
This was recently explicitly confirmed to me by french Ford dealer Fornault. This is also explicit on the Ford 1975 documentation (“Oil class API DS(CD) or range III”)
The idea behind that being the modern oils (API SFCF or higher) for modern diesel engine exhibit a too high TBN (Total Base Number) for those venerable old ladies.
This is related to sulfur proportion, lowered in modern gasoil.
SFCF has a TBN of 12 while SFCD as recommended by Ford has a TBN of 4. As a backup one might consider API CF-4 with a TBN of 8
The curious side effect of this SFCD recommandation is that I now have to look for oils in cheap popular supermarkets and flatly ignore whatever oil is dearer than 10€ for 5 liters. Not always easy to find.