Straight from the owners manual.
Look for three things:

•CJ-4
Oils designated as API CJ-4 are required for the vehicle. The CJ-4 designation can appear either alone or in combination with other American Petroleum Institute (API) designations, such as API CJ-4/SL. These letters show API levels of quality.


•SAE 15W-40
SAE 15W-40 is best for the vehicle. When it is very cold, below −18°C (0°F), use SAE 5W-40 to improve cold starting. These numbers on the oil container show its viscosity, or thickness. Do not use other viscosity oils such as SAE 10W-30, SAE 10W-40, or SAE 20W-50.

•American Petroleum Institute (API) symbol
This doughnut-shaped logo (symbol) is used on most oil containers to help you select the correct oil. It means that the oil has been certified by the American Petroleum Institute.

Look for this on the oil container, and use only those oils that display this logo.

Notice: Use only engine oils that have the designation CJ-4 for the diesel engine. Failure to use the recommended oil can damage the DPF and result in engine damage not covered by the vehicle warranty.

Engine Oil Additives/Engine Oil Flushes
Do not add anything to the oil. The recommended oils with the API service symbol are all that is needed for good performance and engine protection.

Engine oil system flushes are not recommended and could cause engine damage not covered by the vehicle warranty.