Hi I have a 2008 Grand Cherokee with the Merc OM642 Diesel unit in it. I have no DPF fitted, Jeep only fitted them on new model in UK I believe. My oil spec is 229.51.Will I be ok using any Oil that is Merc approved to 229.51 or is it not as simple as that? I am looking for ultimate Engine and Turbo protection rather then fuel economy. What are the ingredients in the oil I should be looking for? Indeed are all 229.51 oils made to the same 'recipe'? Any suggestions on viscosity range? My handbook calls for a 5w-30. The UK has a relatively moderate climate. Forgive me if any of my questions are a little naïve but I am just learning and am finding the subject very interesting. Many thanks. Tikka.