For the last two services on my 2014 Jeep Grand Cherokee 3.0-litre diesel the dealer has used Shell Helix Ultra 5W-40 oil as directed by FCA Aust. This oil is not recommended by Shell to be used in diesel engines fitted with a DPF. The diesel Jeep has a DPF! Previously the oil used was Mobil 1, a low ash DPF
compatible oil. I have tried to contact FCA on two occasions regarding why they are using non-compatible oil and what harm it is doing to the DPF, without response. Do you have any idea what harm this is doing to my engine and exhaust system?