What is your opinion on fully syntehtic DEXOS 2 spec 5W30 oil sold by GM dealers for use in diesel vehicles? is this decent quality oil to be used in Cruze diesel engine? In terms of maintaining the engine warranty, this oil is what GM prefers that we use. The price from my local GM dealer with the discount I get is not bad for this oil - under $ 6/quart. Because this engine eneds just over 5 quarts with the oild filter change, you need to get 6 quarts of oil per oil change. I used this oil for my first oil change. The total cost of 6 quarts of oil and the AC oil filter was about $ 45.