Chances are your diesel car is fitted with a DPF filter so you need to look for an oil that's Mercedes-Benz 229.51 spec, i.e. compatible with DPF filters. Use of a non-DPF compatible diesel oil will clog your DPF filter and potentially ruin it, which will cost you thousands. Penrite Enviro 5W-40 diesel oil meets that spec and is a low / medium ash oil and suitable for use in diesel engines fitted with DPF filters. I run this in my 2007 Mercedes diesel and its a very good full synthetic oil widely available at Supercheap or Repco at a very reasonable price. Its an Australian made oil so you get the feel good factor of supporting an Australian business.
They also make a 5W-30 Enviro which is slightly more expensive but I prefer a 5W-40 viscosity level for a turbo diesel engine.
I have been using Nulon 5-30 in my 300c diesel for quite some time .It meets all the specs and I am now using it on my 2014 diesel Jeep .The Jeep has a much more advanced system and it tells me the oil condition and most importantly it meets all the standards for that engine.
It retails for about $106 per 10 litres at Super cheap but I buy up when they have 20% off.
I even contacted Nulon to get their recommendations because it is not a listed Mopar recommendation but it does meet every standard.
The classic was when I asked the dealer service dept what oil did they use on the Diesel jeeps they said Castrol because they are a multi franchise dealer and Hyundai recommend Castrol!