Found this on the castrol site, I use sometimes. I think what there saying is that this is the oil to use, but must be changed every 10 K miles, 15k KM. I use it myself, but to be honest I dont get many PD customers. Personally I would change it sooner, as the PD system generates large loads on the oil. Definetly sooner if the mileage is higher than 100,000 miles.
http://129.35.64.91/bpglis/lubtds.nsf/tech...24?OpenDocument
John
http://129.35.64.91/bpglis/lubtds.nsf/tech...24?OpenDocument
John